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webkit / WebKit / 9765eaae75bc2c2ccc4b2468231acc50588e5d25 / . / JavaScriptCore / wtf / FastMalloc.cpp
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// Copyright (c) 2005, 2007, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
// Author: Sanjay Ghemawat <opensource@google.com>
//
// A malloc that uses a per-thread cache to satisfy small malloc requests.
// (The time for malloc/free of a small object drops from 300 ns to 50 ns.)
//
// See doc/tcmalloc.html for a high-level
// description of how this malloc works.
//
// SYNCHRONIZATION
// 1. The thread-specific lists are accessed without acquiring any locks.
// This is safe because each such list is only accessed by one thread.
// 2. We have a lock per central free-list, and hold it while manipulating
// the central free list for a particular size.
// 3. The central page allocator is protected by "pageheap_lock".
// 4. The pagemap (which maps from page-number to descriptor),
// can be read without holding any locks, and written while holding
// the "pageheap_lock".
// 5. To improve performance, a subset of the information one can get
// from the pagemap is cached in a data structure, pagemap_cache_,
// that atomically reads and writes its entries. This cache can be
// read and written without locking.
//
// This multi-threaded access to the pagemap is safe for fairly
// subtle reasons. We basically assume that when an object X is
// allocated by thread A and deallocated by thread B, there must
// have been appropriate synchronization in the handoff of object
// X from thread A to thread B. The same logic applies to pagemap_cache_.
//
// THE PAGEID-TO-SIZECLASS CACHE
// Hot PageID-to-sizeclass mappings are held by pagemap_cache_. If this cache
// returns 0 for a particular PageID then that means "no information," not that
// the sizeclass is 0. The cache may have stale information for pages that do
// not hold the beginning of any free()'able object. Staleness is eliminated
// in Populate() for pages with sizeclass > 0 objects, and in do_malloc() and
// do_memalign() for all other relevant pages.
//
// TODO: Bias reclamation to larger addresses
// TODO: implement mallinfo/mallopt
// TODO: Better testing
//
// 9/28/2003 (new page-level allocator replaces ptmalloc2):
// * malloc/free of small objects goes from ~300 ns to ~50 ns.
// * allocation of a reasonably complicated struct
// goes from about 1100 ns to about 300 ns.
#include "config.h"
#include "FastMalloc.h"
#include "Assertions.h"
#if USE(MULTIPLE_THREADS)
#include <pthread.h>
#endif
#ifndef NO_TCMALLOC_SAMPLES
#ifdef WTF_CHANGES
#define NO_TCMALLOC_SAMPLES
#endif
#endif
#if !defined(USE_SYSTEM_MALLOC) && defined(NDEBUG)
#define FORCE_SYSTEM_MALLOC 0
#else
#define FORCE_SYSTEM_MALLOC 1
#endif
#ifndef NDEBUG
namespace WTF {
#if USE(MULTIPLE_THREADS)
static pthread_key_t isForbiddenKey;
static pthread_once_t isForbiddenKeyOnce = PTHREAD_ONCE_INIT;
static void initializeIsForbiddenKey()
{
pthread_key_create(&isForbiddenKey, 0);
}
static bool isForbidden()
{
pthread_once(&isForbiddenKeyOnce, initializeIsForbiddenKey);
return !!pthread_getspecific(isForbiddenKey);
}
void fastMallocForbid()
{
pthread_once(&isForbiddenKeyOnce, initializeIsForbiddenKey);
pthread_setspecific(isForbiddenKey, &isForbiddenKey);
}
void fastMallocAllow()
{
pthread_once(&isForbiddenKeyOnce, initializeIsForbiddenKey);
pthread_setspecific(isForbiddenKey, 0);
}
#else
static bool staticIsForbidden;
static bool isForbidden()
{
return staticIsForbidden;
}
void fastMallocForbid()
{
staticIsForbidden = true;
}
void fastMallocAllow()
{
staticIsForbidden = false;
}
#endif // USE(MULTIPLE_THREADS)
} // namespace WTF
#endif // NDEBUG
#include <string.h>
namespace WTF {
void *fastZeroedMalloc(size_t n)
{
void *result = fastMalloc(n);
if (!result)
return 0;
memset(result, 0, n);
#ifndef WTF_CHANGES
MallocHook::InvokeNewHook(result, n);
#endif
return result;
}
}
#if FORCE_SYSTEM_MALLOC
#include <stdlib.h>
#if !PLATFORM(WIN_OS)
#include <pthread.h>
#endif
namespace WTF {
void *fastMalloc(size_t n)
{
ASSERT(!isForbidden());
return malloc(n);
}
void *fastCalloc(size_t n_elements, size_t element_size)
{
ASSERT(!isForbidden());
return calloc(n_elements, element_size);
}
void fastFree(void* p)
{
ASSERT(!isForbidden());
free(p);
}
void *fastRealloc(void* p, size_t n)
{
ASSERT(!isForbidden());
return realloc(p, n);
}
} // namespace WTF
#if PLATFORM(DARWIN)
// This symbol is present in the JavaScriptCore exports file even when FastMalloc is disabled.
// It will never be used in this case, so it's type and value are less interesting than its presence.
extern "C" const int jscore_fastmalloc_introspection = 0;
#endif
#else
#if HAVE(STDINT_H)
#include <stdint.h>
#elif HAVE(INTTYPES_H)
#include <inttypes.h>
#else
#include <sys/types.h>
#endif
#include "AlwaysInline.h"
#include "Assertions.h"
#include "TCPackedCache.h"
#include "TCPageMap.h"
#include "TCSpinLock.h"
#include "TCSystemAlloc.h"
#include <algorithm>
#include <errno.h>
#include <new>
#include <pthread.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#if COMPILER(MSVC)
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#endif
#if WTF_CHANGES
#if PLATFORM(DARWIN)
#include "MallocZoneSupport.h"
#endif
#ifndef PRIuS
#define PRIuS "zu"
#endif
// Calling pthread_getspecific through a global function pointer is faster than a normal
// call to the function on Mac OS X, and it's used in performance-critical code. So we
// use a function pointer. But that's not necessarily faster on other platforms, and we had
// problems with this technique on Windows, so we'll do this only on Mac OS X.
#if PLATFORM(DARWIN)
static void* (*pthread_getspecific_function_pointer)(pthread_key_t) = pthread_getspecific;
#define pthread_getspecific(key) pthread_getspecific_function_pointer(key)
#endif
#define DEFINE_VARIABLE(type, name, value, meaning) \
namespace FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead { \
type FLAGS_##name(value); \
char FLAGS_no##name; \
} \
using FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead::FLAGS_##name
#define DEFINE_int64(name, value, meaning) \
DEFINE_VARIABLE(int64_t, name, value, meaning)
#define DEFINE_double(name, value, meaning) \
DEFINE_VARIABLE(double, name, value, meaning)
namespace WTF {
#define malloc fastMalloc
#define calloc fastCalloc
#define free fastFree
#define realloc fastRealloc
#define MESSAGE LOG_ERROR
#define CHECK_CONDITION ASSERT
#if PLATFORM(DARWIN)
class TCMalloc_PageHeap;
class TCMalloc_ThreadCache;
class TCMalloc_Central_FreeListPadded;
class FastMallocZone {
public:
static void init();
static kern_return_t enumerate(task_t, void*, unsigned typeMmask, vm_address_t zoneAddress, memory_reader_t, vm_range_recorder_t);
static size_t goodSize(malloc_zone_t*, size_t size) { return size; }
static boolean_t check(malloc_zone_t*) { return true; }
static void print(malloc_zone_t*, boolean_t) { }
static void log(malloc_zone_t*, void*) { }
static void forceLock(malloc_zone_t*) { }
static void forceUnlock(malloc_zone_t*) { }
static void statistics(malloc_zone_t*, malloc_statistics_t*) { }
private:
FastMallocZone(TCMalloc_PageHeap*, TCMalloc_ThreadCache**, TCMalloc_Central_FreeListPadded*);
static size_t size(malloc_zone_t*, const void*);
static void* zoneMalloc(malloc_zone_t*, size_t);
static void* zoneCalloc(malloc_zone_t*, size_t numItems, size_t size);
static void zoneFree(malloc_zone_t*, void*);
static void* zoneRealloc(malloc_zone_t*, void*, size_t);
static void* zoneValloc(malloc_zone_t*, size_t) { LOG_ERROR("valloc is not supported"); return 0; }
static void zoneDestroy(malloc_zone_t*) { }
malloc_zone_t m_zone;
TCMalloc_PageHeap* m_pageHeap;
TCMalloc_ThreadCache** m_threadHeaps;
TCMalloc_Central_FreeListPadded* m_centralCaches;
};
#endif
#endif
#ifndef WTF_CHANGES
// This #ifdef should almost never be set. Set NO_TCMALLOC_SAMPLES if
// you're porting to a system where you really can't get a stacktrace.
#ifdef NO_TCMALLOC_SAMPLES
// We use #define so code compiles even if you #include stacktrace.h somehow.
# define GetStackTrace(stack, depth, skip) (0)
#else
# include <google/stacktrace.h>
#endif
#endif
// Even if we have support for thread-local storage in the compiler
// and linker, the OS may not support it. We need to check that at
// runtime. Right now, we have to keep a manual set of "bad" OSes.
#if defined(HAVE_TLS)
static bool kernel_supports_tls = false; // be conservative
static inline bool KernelSupportsTLS() {
return kernel_supports_tls;
}
# if !HAVE_DECL_UNAME // if too old for uname, probably too old for TLS
static void CheckIfKernelSupportsTLS() {
kernel_supports_tls = false;
}
# else
# include <sys/utsname.h> // DECL_UNAME checked for <sys/utsname.h> too
static void CheckIfKernelSupportsTLS() {
struct utsname buf;
if (uname(&buf) != 0) { // should be impossible
MESSAGE("uname failed assuming no TLS support (errno=%d)\n", errno);
kernel_supports_tls = false;
} else if (strcasecmp(buf.sysname, "linux") == 0) {
// The linux case: the first kernel to support TLS was 2.6.0
if (buf.release[0] < '2' && buf.release[1] == '.') // 0.x or 1.x
kernel_supports_tls = false;
else if (buf.release[0] == '2' && buf.release[1] == '.' &&
buf.release[2] >= '0' && buf.release[2] < '6' &&
buf.release[3] == '.') // 2.0 - 2.5
kernel_supports_tls = false;
else
kernel_supports_tls = true;
} else { // some other kernel, we'll be optimisitic
kernel_supports_tls = true;
}
// TODO(csilvers): VLOG(1) the tls status once we support RAW_VLOG
}
# endif // HAVE_DECL_UNAME
#endif // HAVE_TLS
// __THROW is defined in glibc systems. It means, counter-intuitively,
// "This function will never throw an exception." It's an optional
// optimization tool, but we may need to use it to match glibc prototypes.
#ifndef __THROW // I guess we're not on a glibc system
# define __THROW // __THROW is just an optimization, so ok to make it ""
#endif
//-------------------------------------------------------------------
// Configuration
//-------------------------------------------------------------------
// Not all possible combinations of the following parameters make
// sense. In particular, if kMaxSize increases, you may have to
// increase kNumClasses as well.
static const size_t kPageShift = 12;
static const size_t kPageSize = 1 << kPageShift;
static const size_t kMaxSize = 8u * kPageSize;
static const size_t kAlignShift = 3;
static const size_t kAlignment = 1 << kAlignShift;
static const size_t kNumClasses = 68;
// Allocates a big block of memory for the pagemap once we reach more than
// 128MB
static const size_t kPageMapBigAllocationThreshold = 128 << 20;
// Minimum number of pages to fetch from system at a time. Must be
// significantly bigger than kBlockSize to amortize system-call
// overhead, and also to reduce external fragementation. Also, we
// should keep this value big because various incarnations of Linux
// have small limits on the number of mmap() regions per
// address-space.
static const size_t kMinSystemAlloc = 1 << (20 - kPageShift);
// Number of objects to move between a per-thread list and a central
// list in one shot. We want this to be not too small so we can
// amortize the lock overhead for accessing the central list. Making
// it too big may temporarily cause unnecessary memory wastage in the
// per-thread free list until the scavenger cleans up the list.
static int num_objects_to_move[kNumClasses];
// Maximum length we allow a per-thread free-list to have before we
// move objects from it into the corresponding central free-list. We
// want this big to avoid locking the central free-list too often. It
// should not hurt to make this list somewhat big because the
// scavenging code will shrink it down when its contents are not in use.
static const int kMaxFreeListLength = 256;
// Lower and upper bounds on the per-thread cache sizes
static const size_t kMinThreadCacheSize = kMaxSize * 2;
static const size_t kMaxThreadCacheSize = 2 << 20;
// Default bound on the total amount of thread caches
static const size_t kDefaultOverallThreadCacheSize = 16 << 20;
// For all span-lengths < kMaxPages we keep an exact-size list.
// REQUIRED: kMaxPages >= kMinSystemAlloc;
static const size_t kMaxPages = kMinSystemAlloc;
/* The smallest prime > 2^n */
static int primes_list[] = {
// Small values might cause high rates of sampling
// and hence commented out.
// 2, 5, 11, 17, 37, 67, 131, 257,
// 521, 1031, 2053, 4099, 8209, 16411,
32771, 65537, 131101, 262147, 524309, 1048583,
2097169, 4194319, 8388617, 16777259, 33554467 };
// Twice the approximate gap between sampling actions.
// I.e., we take one sample approximately once every
// tcmalloc_sample_parameter/2
// bytes of allocation, i.e., ~ once every 128KB.
// Must be a prime number.
#ifdef NO_TCMALLOC_SAMPLES
DEFINE_int64(tcmalloc_sample_parameter, 0,
"Unused: code is compiled with NO_TCMALLOC_SAMPLES");
static size_t sample_period = 0;
#else
DEFINE_int64(tcmalloc_sample_parameter, 262147,
"Twice the approximate gap between sampling actions."
" Must be a prime number. Otherwise will be rounded up to a "
" larger prime number");
static size_t sample_period = 262147;
#endif
// Protects sample_period above
static SpinLock sample_period_lock = SPINLOCK_INITIALIZER;
// Parameters for controlling how fast memory is returned to the OS.
DEFINE_double(tcmalloc_release_rate, 1,
"Rate at which we release unused memory to the system. "
"Zero means we never release memory back to the system. "
"Increase this flag to return memory faster; decrease it "
"to return memory slower. Reasonable rates are in the "
"range [0,10]");
//-------------------------------------------------------------------
// Mapping from size to size_class and vice versa
//-------------------------------------------------------------------
// Sizes <= 1024 have an alignment >= 8. So for such sizes we have an
// array indexed by ceil(size/8). Sizes > 1024 have an alignment >= 128.
// So for these larger sizes we have an array indexed by ceil(size/128).
//
// We flatten both logical arrays into one physical array and use
// arithmetic to compute an appropriate index. The constants used by
// ClassIndex() were selected to make the flattening work.
//
// Examples:
// Size Expression Index
// -------------------------------------------------------
// 0 (0 + 7) / 8 0
// 1 (1 + 7) / 8 1
// ...
// 1024 (1024 + 7) / 8 128
// 1025 (1025 + 127 + (120<<7)) / 128 129
// ...
// 32768 (32768 + 127 + (120<<7)) / 128 376
static const size_t kMaxSmallSize = 1024;
static const int shift_amount[2] = { 3, 7 }; // For divides by 8 or 128
static const int add_amount[2] = { 7, 127 + (120 << 7) };
static unsigned char class_array[377];
// Compute index of the class_array[] entry for a given size
static inline int ClassIndex(size_t s) {
const int i = (s > kMaxSmallSize);
return static_cast<int>((s + add_amount[i]) >> shift_amount[i]);
}
// Mapping from size class to max size storable in that class
static size_t class_to_size[kNumClasses];
// Mapping from size class to number of pages to allocate at a time
static size_t class_to_pages[kNumClasses];
// TransferCache is used to cache transfers of num_objects_to_move[size_class]
// back and forth between thread caches and the central cache for a given size
// class.
struct TCEntry {
void *head; // Head of chain of objects.
void *tail; // Tail of chain of objects.
};
// A central cache freelist can have anywhere from 0 to kNumTransferEntries
// slots to put link list chains into. To keep memory usage bounded the total
// number of TCEntries across size classes is fixed. Currently each size
// class is initially given one TCEntry which also means that the maximum any
// one class can have is kNumClasses.
static const int kNumTransferEntries = kNumClasses;
// Note: the following only works for "n"s that fit in 32-bits, but
// that is fine since we only use it for small sizes.
static inline int LgFloor(size_t n) {
int log = 0;
for (int i = 4; i >= 0; --i) {
int shift = (1 << i);
size_t x = n >> shift;
if (x != 0) {
n = x;
log += shift;
}
}
ASSERT(n == 1);
return log;
}
// Some very basic linked list functions for dealing with using void * as
// storage.
static inline void *SLL_Next(void *t) {
return *(reinterpret_cast<void**>(t));
}
static inline void SLL_SetNext(void *t, void *n) {
*(reinterpret_cast<void**>(t)) = n;
}
static inline void SLL_Push(void **list, void *element) {
SLL_SetNext(element, *list);
*list = element;
}
static inline void *SLL_Pop(void **list) {
void *result = *list;
*list = SLL_Next(*list);
return result;
}
// Remove N elements from a linked list to which head points. head will be
// modified to point to the new head. start and end will point to the first
// and last nodes of the range. Note that end will point to NULL after this
// function is called.
static inline void SLL_PopRange(void **head, int N, void **start, void **end) {
if (N == 0) {
*start = NULL;
*end = NULL;
return;
}
void *tmp = *head;
for (int i = 1; i < N; ++i) {
tmp = SLL_Next(tmp);
}
*start = *head;
*end = tmp;
*head = SLL_Next(tmp);
// Unlink range from list.
SLL_SetNext(tmp, NULL);
}
static inline void SLL_PushRange(void **head, void *start, void *end) {
if (!start) return;
SLL_SetNext(end, *head);
*head = start;
}
static inline size_t SLL_Size(void *head) {
int count = 0;
while (head) {
count++;
head = SLL_Next(head);
}
return count;
}
// Setup helper functions.
static ALWAYS_INLINE size_t SizeClass(size_t size) {
return class_array[ClassIndex(size)];
}
// Get the byte-size for a specified class
static ALWAYS_INLINE size_t ByteSizeForClass(size_t cl) {
return class_to_size[cl];
}
static int NumMoveSize(size_t size) {
if (size == 0) return 0;
// Use approx 64k transfers between thread and central caches.
int num = static_cast<int>(64.0 * 1024.0 / size);
if (num < 2) num = 2;
// Clamp well below kMaxFreeListLength to avoid ping pong between central
// and thread caches.
if (num > static_cast<int>(0.8 * kMaxFreeListLength))
num = static_cast<int>(0.8 * kMaxFreeListLength);
// Also, avoid bringing in too many objects into small object free
// lists. There are lots of such lists, and if we allow each one to
// fetch too many at a time, we end up having to scavenge too often
// (especially when there are lots of threads and each thread gets a
// small allowance for its thread cache).
//
// TODO: Make thread cache free list sizes dynamic so that we do not
// have to equally divide a fixed resource amongst lots of threads.
if (num > 32) num = 32;
return num;
}
// Initialize the mapping arrays
static void InitSizeClasses() {
// Do some sanity checking on add_amount[]/shift_amount[]/class_array[]
if (ClassIndex(0) < 0) {
MESSAGE("Invalid class index %d for size 0\n", ClassIndex(0));
abort();
}
if (static_cast<size_t>(ClassIndex(kMaxSize)) >= sizeof(class_array)) {
MESSAGE("Invalid class index %d for kMaxSize\n", ClassIndex(kMaxSize));
abort();
}
// Compute the size classes we want to use
size_t sc = 1; // Next size class to assign
unsigned char alignshift = kAlignShift;
int last_lg = -1;
for (size_t size = kAlignment; size <= kMaxSize; size += (1 << alignshift)) {
int lg = LgFloor(size);
if (lg > last_lg) {
// Increase alignment every so often.
//
// Since we double the alignment every time size doubles and
// size >= 128, this means that space wasted due to alignment is
// at most 16/128 i.e., 12.5%. Plus we cap the alignment at 256
// bytes, so the space wasted as a percentage starts falling for
// sizes > 2K.
if ((lg >= 7) && (alignshift < 8)) {
alignshift++;
}
last_lg = lg;
}
// Allocate enough pages so leftover is less than 1/8 of total.
// This bounds wasted space to at most 12.5%.
size_t psize = kPageSize;
while ((psize % size) > (psize >> 3)) {
psize += kPageSize;
}
const size_t my_pages = psize >> kPageShift;
if (sc > 1 && my_pages == class_to_pages[sc-1]) {
// See if we can merge this into the previous class without
// increasing the fragmentation of the previous class.
const size_t my_objects = (my_pages << kPageShift) / size;
const size_t prev_objects = (class_to_pages[sc-1] << kPageShift)
/ class_to_size[sc-1];
if (my_objects == prev_objects) {
// Adjust last class to include this size
class_to_size[sc-1] = size;
continue;
}
}
// Add new class
class_to_pages[sc] = my_pages;
class_to_size[sc] = size;
sc++;
}
if (sc != kNumClasses) {
MESSAGE("wrong number of size classes: found %" PRIuS " instead of %d\n",
sc, int(kNumClasses));
abort();
}
// Initialize the mapping arrays
int next_size = 0;
for (unsigned char c = 1; c < kNumClasses; c++) {
const size_t max_size_in_class = class_to_size[c];
for (size_t s = next_size; s <= max_size_in_class; s += kAlignment) {
class_array[ClassIndex(s)] = c;
}
next_size = static_cast<int>(max_size_in_class + kAlignment);
}
// Double-check sizes just to be safe
for (size_t size = 0; size <= kMaxSize; size++) {
const size_t sc = SizeClass(size);
if (sc == 0) {
MESSAGE("Bad size class %" PRIuS " for %" PRIuS "\n", sc, size);
abort();
}
if (sc > 1 && size <= class_to_size[sc-1]) {
MESSAGE("Allocating unnecessarily large class %" PRIuS " for %" PRIuS
"\n", sc, size);
abort();
}
if (sc >= kNumClasses) {
MESSAGE("Bad size class %" PRIuS " for %" PRIuS "\n", sc, size);
abort();
}
const size_t s = class_to_size[sc];
if (size > s) {
MESSAGE("Bad size %" PRIuS " for %" PRIuS " (sc = %" PRIuS ")\n", s, size, sc);
abort();
}
if (s == 0) {
MESSAGE("Bad size %" PRIuS " for %" PRIuS " (sc = %" PRIuS ")\n", s, size, sc);
abort();
}
}
// Initialize the num_objects_to_move array.
for (size_t cl = 1; cl < kNumClasses; ++cl) {
num_objects_to_move[cl] = NumMoveSize(ByteSizeForClass(cl));
}
#ifndef WTF_CHANGES
if (false) {
// Dump class sizes and maximum external wastage per size class
for (size_t cl = 1; cl < kNumClasses; ++cl) {
const int alloc_size = class_to_pages[cl] << kPageShift;
const int alloc_objs = alloc_size / class_to_size[cl];
const int min_used = (class_to_size[cl-1] + 1) * alloc_objs;
const int max_waste = alloc_size - min_used;
MESSAGE("SC %3d [ %8d .. %8d ] from %8d ; %2.0f%% maxwaste\n",
int(cl),
int(class_to_size[cl-1] + 1),
int(class_to_size[cl]),
int(class_to_pages[cl] << kPageShift),
max_waste * 100.0 / alloc_size
);
}
}
#endif
}
// -------------------------------------------------------------------------
// Simple allocator for objects of a specified type. External locking
// is required before accessing one of these objects.
// -------------------------------------------------------------------------
// Metadata allocator -- keeps stats about how many bytes allocated
static uint64_t metadata_system_bytes = 0;
static void* MetaDataAlloc(size_t bytes) {
void* result = TCMalloc_SystemAlloc(bytes, 0);
if (result != NULL) {
metadata_system_bytes += bytes;
}
return result;
}
template <class T>
class PageHeapAllocator {
private:
// How much to allocate from system at a time
static const size_t kAllocIncrement = 32 << 10;
// Aligned size of T
static const size_t kAlignedSize
= (((sizeof(T) + kAlignment - 1) / kAlignment) * kAlignment);
// Free area from which to carve new objects
char* free_area_;
size_t free_avail_;
// Free list of already carved objects
void* free_list_;
// Number of allocated but unfreed objects
int inuse_;
public:
void Init() {
ASSERT(kAlignedSize <= kAllocIncrement);
inuse_ = 0;
free_area_ = NULL;
free_avail_ = 0;
free_list_ = NULL;
}
T* New() {
// Consult free list
void* result;
if (free_list_ != NULL) {
result = free_list_;
free_list_ = *(reinterpret_cast<void**>(result));
} else {
if (free_avail_ < kAlignedSize) {
// Need more room
free_area_ = reinterpret_cast<char*>(MetaDataAlloc(kAllocIncrement));
if (free_area_ == NULL) abort();
free_avail_ = kAllocIncrement;
}
result = free_area_;
free_area_ += kAlignedSize;
free_avail_ -= kAlignedSize;
}
inuse_++;
return reinterpret_cast<T*>(result);
}
void Delete(T* p) {
*(reinterpret_cast<void**>(p)) = free_list_;
free_list_ = p;
inuse_--;
}
int inuse() const { return inuse_; }
};
// -------------------------------------------------------------------------
// Span - a contiguous run of pages
// -------------------------------------------------------------------------
// Type that can hold a page number
typedef uintptr_t PageID;
// Type that can hold the length of a run of pages
typedef uintptr_t Length;
static const Length kMaxValidPages = (~static_cast<Length>(0)) >> kPageShift;
// Convert byte size into pages. This won't overflow, but may return
// an unreasonably large value if bytes is huge enough.
static inline Length pages(size_t bytes) {
return (bytes >> kPageShift) +
((bytes & (kPageSize - 1)) > 0 ? 1 : 0);
}
// Convert a user size into the number of bytes that will actually be
// allocated
static size_t AllocationSize(size_t bytes) {
if (bytes > kMaxSize) {
// Large object: we allocate an integral number of pages
ASSERT(bytes <= (kMaxValidPages << kPageShift));
return pages(bytes) << kPageShift;
} else {
// Small object: find the size class to which it belongs
return ByteSizeForClass(SizeClass(bytes));
}
}
// Information kept for a span (a contiguous run of pages).
struct Span {
PageID start; // Starting page number
Length length; // Number of pages in span
Span* next; // Used when in link list
Span* prev; // Used when in link list
void* objects; // Linked list of free objects
unsigned int free : 1; // Is the span free
unsigned int sample : 1; // Sampled object?
unsigned int sizeclass : 8; // Size-class for small objects (or 0)
unsigned int refcount : 11; // Number of non-free objects
#undef SPAN_HISTORY
#ifdef SPAN_HISTORY
// For debugging, we can keep a log events per span
int nexthistory;
char history[64];
int value[64];
#endif
};
#ifdef SPAN_HISTORY
void Event(Span* span, char op, int v = 0) {
span->history[span->nexthistory] = op;
span->value[span->nexthistory] = v;
span->nexthistory++;
if (span->nexthistory == sizeof(span->history)) span->nexthistory = 0;
}
#else
#define Event(s,o,v) ((void) 0)
#endif
// Allocator/deallocator for spans
static PageHeapAllocator<Span> span_allocator;
static Span* NewSpan(PageID p, Length len) {
Span* result = span_allocator.New();
memset(result, 0, sizeof(*result));
result->start = p;
result->length = len;
#ifdef SPAN_HISTORY
result->nexthistory = 0;
#endif
return result;
}
static inline void DeleteSpan(Span* span) {
#ifndef NDEBUG
// In debug mode, trash the contents of deleted Spans
memset(span, 0x3f, sizeof(*span));
#endif
span_allocator.Delete(span);
}
// -------------------------------------------------------------------------
// Doubly linked list of spans.
// -------------------------------------------------------------------------
static inline void DLL_Init(Span* list) {
list->next = list;
list->prev = list;
}
static inline void DLL_Remove(Span* span) {
span->prev->next = span->next;
span->next->prev = span->prev;
span->prev = NULL;
span->next = NULL;
}
static ALWAYS_INLINE bool DLL_IsEmpty(const Span* list) {
return list->next == list;
}
#ifndef WTF_CHANGES
static int DLL_Length(const Span* list) {
int result = 0;
for (Span* s = list->next; s != list; s = s->next) {
result++;
}
return result;
}
#endif
#if 0 /* Not needed at the moment -- causes compiler warnings if not used */
static void DLL_Print(const char* label, const Span* list) {
MESSAGE("%-10s %p:", label, list);
for (const Span* s = list->next; s != list; s = s->next) {
MESSAGE(" <%p,%u,%u>", s, s->start, s->length);
}
MESSAGE("\n");
}
#endif
static inline void DLL_Prepend(Span* list, Span* span) {
ASSERT(span->next == NULL);
ASSERT(span->prev == NULL);
span->next = list->next;
span->prev = list;
list->next->prev = span;
list->next = span;
}
// -------------------------------------------------------------------------
// Stack traces kept for sampled allocations
// The following state is protected by pageheap_lock_.
// -------------------------------------------------------------------------
// size/depth are made the same size as a pointer so that some generic
// code below can conveniently cast them back and forth to void*.
static const int kMaxStackDepth = 31;
struct StackTrace {
uintptr_t size; // Size of object
uintptr_t depth; // Number of PC values stored in array below
void* stack[kMaxStackDepth];
};
static PageHeapAllocator<StackTrace> stacktrace_allocator;
static Span sampled_objects;
// -------------------------------------------------------------------------
// Map from page-id to per-page data
// -------------------------------------------------------------------------
// We use PageMap2<> for 32-bit and PageMap3<> for 64-bit machines.
// We also use a simple one-level cache for hot PageID-to-sizeclass mappings,
// because sometimes the sizeclass is all the information we need.
// Selector class -- general selector uses 3-level map
template <int BITS> class MapSelector {
public:
typedef TCMalloc_PageMap3<BITS-kPageShift> Type;
typedef PackedCache<BITS, uint64_t> CacheType;
};
// A two-level map for 32-bit machines
template <> class MapSelector<32> {
public:
typedef TCMalloc_PageMap2<32-kPageShift> Type;
typedef PackedCache<32-kPageShift, uint16_t> CacheType;
};
// -------------------------------------------------------------------------
// Page-level allocator
// * Eager coalescing
//
// Heap for page-level allocation. We allow allocating and freeing a
// contiguous runs of pages (called a "span").
// -------------------------------------------------------------------------
class TCMalloc_PageHeap {
public:
void init();
// Allocate a run of "n" pages. Returns zero if out of memory.
Span* New(Length n);
// Delete the span "[p, p+n-1]".
// REQUIRES: span was returned by earlier call to New() and
// has not yet been deleted.
void Delete(Span* span);
// Mark an allocated span as being used for small objects of the
// specified size-class.
// REQUIRES: span was returned by an earlier call to New()
// and has not yet been deleted.
void RegisterSizeClass(Span* span, size_t sc);
// Split an allocated span into two spans: one of length "n" pages
// followed by another span of length "span->length - n" pages.
// Modifies "*span" to point to the first span of length "n" pages.
// Returns a pointer to the second span.
//
// REQUIRES: "0 < n < span->length"
// REQUIRES: !span->free
// REQUIRES: span->sizeclass == 0
Span* Split(Span* span, Length n);
// Return the descriptor for the specified page.
inline Span* GetDescriptor(PageID p) const {
return reinterpret_cast<Span*>(pagemap_.get(p));
}
#ifdef WTF_CHANGES
inline Span* GetDescriptorEnsureSafe(PageID p)
{
pagemap_.Ensure(p, 1);
return GetDescriptor(p);
}
#endif
// Dump state to stderr
#ifndef WTF_CHANGES
void Dump(TCMalloc_Printer* out);
#endif
// Return number of bytes allocated from system
inline uint64_t SystemBytes() const { return system_bytes_; }
// Return number of free bytes in heap
uint64_t FreeBytes() const {
return (static_cast<uint64_t>(free_pages_) << kPageShift);
}
bool Check();
bool CheckList(Span* list, Length min_pages, Length max_pages);
// Release all pages on the free list for reuse by the OS:
void ReleaseFreePages();
// Return 0 if we have no information, or else the correct sizeclass for p.
// Reads and writes to pagemap_cache_ do not require locking.
// The entries are 64 bits on 64-bit hardware and 16 bits on
// 32-bit hardware, and we don't mind raciness as long as each read of
// an entry yields a valid entry, not a partially updated entry.
size_t GetSizeClassIfCached(PageID p) const {
return pagemap_cache_.GetOrDefault(p, 0);
}
void CacheSizeClass(PageID p, size_t cl) const { pagemap_cache_.Put(p, cl); }
private:
// Pick the appropriate map and cache types based on pointer size
typedef MapSelector<8*sizeof(uintptr_t)>::Type PageMap;
typedef MapSelector<8*sizeof(uintptr_t)>::CacheType PageMapCache;
PageMap pagemap_;
mutable PageMapCache pagemap_cache_;
// We segregate spans of a given size into two circular linked
// lists: one for normal spans, and one for spans whose memory
// has been returned to the system.
struct SpanList {
Span normal;
Span returned;
};
// List of free spans of length >= kMaxPages
SpanList large_;
// Array mapping from span length to a doubly linked list of free spans
SpanList free_[kMaxPages];
// Number of pages kept in free lists
uintptr_t free_pages_;
// Bytes allocated from system
uint64_t system_bytes_;
bool GrowHeap(Length n);
// REQUIRES span->length >= n
// Remove span from its free list, and move any leftover part of
// span into appropriate free lists. Also update "span" to have
// length exactly "n" and mark it as non-free so it can be returned
// to the client.
//
// "released" is true iff "span" was found on a "returned" list.
void Carve(Span* span, Length n, bool released);
void RecordSpan(Span* span) {
pagemap_.set(span->start, span);
if (span->length > 1) {
pagemap_.set(span->start + span->length - 1, span);
}
}
// Allocate a large span of length == n. If successful, returns a
// span of exactly the specified length. Else, returns NULL.
Span* AllocLarge(Length n);
// Incrementally release some memory to the system.
// IncrementalScavenge(n) is called whenever n pages are freed.
void IncrementalScavenge(Length n);
// Number of pages to deallocate before doing more scavenging
int64_t scavenge_counter_;
// Index of last free list we scavenged
size_t scavenge_index_;
#if defined(WTF_CHANGES) && PLATFORM(DARWIN)
friend class FastMallocZone;
#endif
};
void TCMalloc_PageHeap::init()
{
pagemap_.init(MetaDataAlloc);
pagemap_cache_ = PageMapCache(0);
free_pages_ = 0;
system_bytes_ = 0;
scavenge_counter_ = 0;
// Start scavenging at kMaxPages list
scavenge_index_ = kMaxPages-1;
COMPILE_ASSERT(kNumClasses <= (1 << PageMapCache::kValuebits), valuebits);
DLL_Init(&large_.normal);
DLL_Init(&large_.returned);
for (size_t i = 0; i < kMaxPages; i++) {
DLL_Init(&free_[i].normal);
DLL_Init(&free_[i].returned);
}
}
inline Span* TCMalloc_PageHeap::New(Length n) {
ASSERT(Check());
ASSERT(n > 0);
// Find first size >= n that has a non-empty list
for (Length s = n; s < kMaxPages; s++) {
Span* ll = NULL;
bool released = false;
if (!DLL_IsEmpty(&free_[s].normal)) {
// Found normal span
ll = &free_[s].normal;
} else if (!DLL_IsEmpty(&free_[s].returned)) {
// Found returned span; reallocate it
ll = &free_[s].returned;
released = true;
} else {
// Keep looking in larger classes
continue;
}
Span* result = ll->next;
Carve(result, n, released);
ASSERT(Check());
free_pages_ -= n;
return result;
}
Span* result = AllocLarge(n);
if (result != NULL) return result;
// Grow the heap and try again
if (!GrowHeap(n)) {
ASSERT(Check());
return NULL;
}
return AllocLarge(n);
}
Span* TCMalloc_PageHeap::AllocLarge(Length n) {
// find the best span (closest to n in size).
// The following loops implements address-ordered best-fit.
bool from_released = false;
Span *best = NULL;
// Search through normal list
for (Span* span = large_.normal.next;
span != &large_.normal;
span = span->next) {
if (span->length >= n) {
if ((best == NULL)
|| (span->length < best->length)
|| ((span->length == best->length) && (span->start < best->start))) {
best = span;
from_released = false;
}
}
}
// Search through released list in case it has a better fit
for (Span* span = large_.returned.next;
span != &large_.returned;
span = span->next) {
if (span->length >= n) {
if ((best == NULL)
|| (span->length < best->length)
|| ((span->length == best->length) && (span->start < best->start))) {
best = span;
from_released = true;
}
}
}
if (best != NULL) {
Carve(best, n, from_released);
ASSERT(Check());
free_pages_ -= n;
return best;
}
return NULL;
}
Span* TCMalloc_PageHeap::Split(Span* span, Length n) {
ASSERT(0 < n);
ASSERT(n < span->length);
ASSERT(!span->free);
ASSERT(span->sizeclass == 0);
Event(span, 'T', n);
const Length extra = span->length - n;
Span* leftover = NewSpan(span->start + n, extra);
Event(leftover, 'U', extra);
RecordSpan(leftover);
pagemap_.set(span->start + n - 1, span); // Update map from pageid to span
span->length = n;
return leftover;
}
inline void TCMalloc_PageHeap::Carve(Span* span, Length n, bool released) {
ASSERT(n > 0);
DLL_Remove(span);
span->free = 0;
Event(span, 'A', n);
const int extra = static_cast<int>(span->length - n);
ASSERT(extra >= 0);
if (extra > 0) {
Span* leftover = NewSpan(span->start + n, extra);
leftover->free = 1;
Event(leftover, 'S', extra);
RecordSpan(leftover);
// Place leftover span on appropriate free list
SpanList* listpair = (static_cast<size_t>(extra) < kMaxPages) ? &free_[extra] : &large_;
Span* dst = released ? &listpair->returned : &listpair->normal;
DLL_Prepend(dst, leftover);
span->length = n;
pagemap_.set(span->start + n - 1, span);
}
}
inline void TCMalloc_PageHeap::Delete(Span* span) {
ASSERT(Check());
ASSERT(!span->free);
ASSERT(span->length > 0);
ASSERT(GetDescriptor(span->start) == span);
ASSERT(GetDescriptor(span->start + span->length - 1) == span);
span->sizeclass = 0;
span->sample = 0;
// Coalesce -- we guarantee that "p" != 0, so no bounds checking
// necessary. We do not bother resetting the stale pagemap
// entries for the pieces we are merging together because we only
// care about the pagemap entries for the boundaries.
//
// Note that the spans we merge into "span" may come out of
// a "returned" list. For simplicity, we move these into the
// "normal" list of the appropriate size class.
const PageID p = span->start;
const Length n = span->length;
Span* prev = GetDescriptor(p-1);
if (prev != NULL && prev->free) {
// Merge preceding span into this span
ASSERT(prev->start + prev->length == p);
const Length len = prev->length;
DLL_Remove(prev);
DeleteSpan(prev);
span->start -= len;
span->length += len;
pagemap_.set(span->start, span);
Event(span, 'L', len);
}
Span* next = GetDescriptor(p+n);
if (next != NULL && next->free) {
// Merge next span into this span
ASSERT(next->start == p+n);
const Length len = next->length;
DLL_Remove(next);
DeleteSpan(next);
span->length += len;
pagemap_.set(span->start + span->length - 1, span);
Event(span, 'R', len);
}
Event(span, 'D', span->length);
span->free = 1;
if (span->length < kMaxPages) {
DLL_Prepend(&free_[span->length].normal, span);
} else {
DLL_Prepend(&large_.normal, span);
}
free_pages_ += n;
IncrementalScavenge(n);
ASSERT(Check());
}
void TCMalloc_PageHeap::IncrementalScavenge(Length n) {
// Fast path; not yet time to release memory
scavenge_counter_ -= n;
if (scavenge_counter_ >= 0) return; // Not yet time to scavenge
// If there is nothing to release, wait for so many pages before
// scavenging again. With 4K pages, this comes to 16MB of memory.
static const size_t kDefaultReleaseDelay = 1 << 8;
// Find index of free list to scavenge
size_t index = scavenge_index_ + 1;
for (size_t i = 0; i < kMaxPages+1; i++) {
if (index > kMaxPages) index = 0;
SpanList* slist = (index == kMaxPages) ? &large_ : &free_[index];
if (!DLL_IsEmpty(&slist->normal)) {
// Release the last span on the normal portion of this list
Span* s = slist->normal.prev;
DLL_Remove(s);
TCMalloc_SystemRelease(reinterpret_cast<void*>(s->start << kPageShift),
static_cast<size_t>(s->length << kPageShift));
DLL_Prepend(&slist->returned, s);
scavenge_counter_ = std::max<size_t>(64UL, std::min<size_t>(kDefaultReleaseDelay, kDefaultReleaseDelay - (free_pages_ / kDefaultReleaseDelay)));
if (index == kMaxPages && !DLL_IsEmpty(&slist->normal))
scavenge_index_ = index - 1;
else
scavenge_index_ = index;
return;
}
index++;
}
// Nothing to scavenge, delay for a while
scavenge_counter_ = kDefaultReleaseDelay;
}
void TCMalloc_PageHeap::RegisterSizeClass(Span* span, size_t sc) {
// Associate span object with all interior pages as well
ASSERT(!span->free);
ASSERT(GetDescriptor(span->start) == span);
ASSERT(GetDescriptor(span->start+span->length-1) == span);
Event(span, 'C', sc);
span->sizeclass = static_cast<unsigned int>(sc);
for (Length i = 1; i < span->length-1; i++) {
pagemap_.set(span->start+i, span);
}
}
#ifndef WTF_CHANGES
static double PagesToMB(uint64_t pages) {
return (pages << kPageShift) / 1048576.0;
}
void TCMalloc_PageHeap::Dump(TCMalloc_Printer* out) {
int nonempty_sizes = 0;
for (int s = 0; s < kMaxPages; s++) {
if (!DLL_IsEmpty(&free_[s].normal) || !DLL_IsEmpty(&free_[s].returned)) {
nonempty_sizes++;
}
}
out->printf("------------------------------------------------\n");
out->printf("PageHeap: %d sizes; %6.1f MB free\n",
nonempty_sizes, PagesToMB(free_pages_));
out->printf("------------------------------------------------\n");
uint64_t total_normal = 0;
uint64_t total_returned = 0;
for (int s = 0; s < kMaxPages; s++) {
const int n_length = DLL_Length(&free_[s].normal);
const int r_length = DLL_Length(&free_[s].returned);
if (n_length + r_length > 0) {
uint64_t n_pages = s * n_length;
uint64_t r_pages = s * r_length;
total_normal += n_pages;
total_returned += r_pages;
out->printf("%6u pages * %6u spans ~ %6.1f MB; %6.1f MB cum"
"; unmapped: %6.1f MB; %6.1f MB cum\n",
s,
(n_length + r_length),
PagesToMB(n_pages + r_pages),
PagesToMB(total_normal + total_returned),
PagesToMB(r_pages),
PagesToMB(total_returned));
}
}
uint64_t n_pages = 0;
uint64_t r_pages = 0;
int n_spans = 0;
int r_spans = 0;
out->printf("Normal large spans:\n");
for (Span* s = large_.normal.next; s != &large_.normal; s = s->next) {
out->printf(" [ %6" PRIuS " pages ] %6.1f MB\n",
s->length, PagesToMB(s->length));
n_pages += s->length;
n_spans++;
}
out->printf("Unmapped large spans:\n");
for (Span* s = large_.returned.next; s != &large_.returned; s = s->next) {
out->printf(" [ %6" PRIuS " pages ] %6.1f MB\n",
s->length, PagesToMB(s->length));
r_pages += s->length;
r_spans++;
}
total_normal += n_pages;
total_returned += r_pages;
out->printf(">255 large * %6u spans ~ %6.1f MB; %6.1f MB cum"
"; unmapped: %6.1f MB; %6.1f MB cum\n",
(n_spans + r_spans),
PagesToMB(n_pages + r_pages),
PagesToMB(total_normal + total_returned),
PagesToMB(r_pages),
PagesToMB(total_returned));
}
#endif
bool TCMalloc_PageHeap::GrowHeap(Length n) {
ASSERT(kMaxPages >= kMinSystemAlloc);
if (n > kMaxValidPages) return false;
Length ask = (n>kMinSystemAlloc) ? n : static_cast<Length>(kMinSystemAlloc);
size_t actual_size;
void* ptr = TCMalloc_SystemAlloc(ask << kPageShift, &actual_size, kPageSize);
if (ptr == NULL) {
if (n < ask) {
// Try growing just "n" pages
ask = n;
ptr = TCMalloc_SystemAlloc(ask << kPageShift, &actual_size, kPageSize);;
}
if (ptr == NULL) return false;
}
ask = actual_size >> kPageShift;
uint64_t old_system_bytes = system_bytes_;
system_bytes_ += (ask << kPageShift);
const PageID p = reinterpret_cast<uintptr_t>(ptr) >> kPageShift;
ASSERT(p > 0);
// If we have already a lot of pages allocated, just pre allocate a bunch of
// memory for the page map. This prevents fragmentation by pagemap metadata
// when a program keeps allocating and freeing large blocks.
if (old_system_bytes < kPageMapBigAllocationThreshold
&& system_bytes_ >= kPageMapBigAllocationThreshold) {
pagemap_.PreallocateMoreMemory();
}
// Make sure pagemap_ has entries for all of the new pages.
// Plus ensure one before and one after so coalescing code
// does not need bounds-checking.
if (pagemap_.Ensure(p-1, ask+2)) {
// Pretend the new area is allocated and then Delete() it to
// cause any necessary coalescing to occur.
//
// We do not adjust free_pages_ here since Delete() will do it for us.
Span* span = NewSpan(p, ask);
RecordSpan(span);
Delete(span);
ASSERT(Check());
return true;
} else {
// We could not allocate memory within "pagemap_"
// TODO: Once we can return memory to the system, return the new span
return false;
}
}
bool TCMalloc_PageHeap::Check() {
ASSERT(free_[0].normal.next == &free_[0].normal);
ASSERT(free_[0].returned.next == &free_[0].returned);
CheckList(&large_.normal, kMaxPages, 1000000000);
CheckList(&large_.returned, kMaxPages, 1000000000);
for (Length s = 1; s < kMaxPages; s++) {
CheckList(&free_[s].normal, s, s);
CheckList(&free_[s].returned, s, s);
}
return true;
}
#if ASSERT_DISABLED
bool TCMalloc_PageHeap::CheckList(Span*, Length, Length) {
return true;
}
#else
bool TCMalloc_PageHeap::CheckList(Span* list, Length min_pages, Length max_pages) {
for (Span* s = list->next; s != list; s = s->next) {
CHECK_CONDITION(s->free);
CHECK_CONDITION(s->length >= min_pages);
CHECK_CONDITION(s->length <= max_pages);
CHECK_CONDITION(GetDescriptor(s->start) == s);
CHECK_CONDITION(GetDescriptor(s->start+s->length-1) == s);
}
return true;
}
#endif
static void ReleaseFreeList(Span* list, Span* returned) {
// Walk backwards through list so that when we push these
// spans on the "returned" list, we preserve the order.
while (!DLL_IsEmpty(list)) {
Span* s = list->prev;
DLL_Remove(s);
DLL_Prepend(returned, s);
TCMalloc_SystemRelease(reinterpret_cast<void*>(s->start << kPageShift),
static_cast<size_t>(s->length << kPageShift));
}
}
void TCMalloc_PageHeap::ReleaseFreePages() {
for (Length s = 0; s < kMaxPages; s++) {
ReleaseFreeList(&free_[s].normal, &free_[s].returned);
}
ReleaseFreeList(&large_.normal, &large_.returned);
ASSERT(Check());
}
//-------------------------------------------------------------------
// Free list
//-------------------------------------------------------------------
class TCMalloc_ThreadCache_FreeList {
private:
void* list_; // Linked list of nodes
uint16_t length_; // Current length
uint16_t lowater_; // Low water mark for list length
public:
void Init() {
list_ = NULL;
length_ = 0;
lowater_ = 0;
}
// Return current length of list
int length() const {
return length_;
}
// Is list empty?
bool empty() const {
return list_ == NULL;
}
// Low-water mark management
int lowwatermark() const { return lowater_; }
void clear_lowwatermark() { lowater_ = length_; }
ALWAYS_INLINE void Push(void* ptr) {
SLL_Push(&list_, ptr);
length_++;
}
void PushRange(int N, void *start, void *end) {
SLL_PushRange(&list_, start, end);
length_ = length_ + static_cast<uint16_t>(N);
}
void PopRange(int N, void **start, void **end) {
SLL_PopRange(&list_, N, start, end);
ASSERT(length_ >= N);
length_ = length_ - static_cast<uint16_t>(N);
if (length_ < lowater_) lowater_ = length_;
}
ALWAYS_INLINE void* Pop() {
ASSERT(list_ != NULL);
length_--;
if (length_ < lowater_) lowater_ = length_;
return SLL_Pop(&list_);
}
#ifdef WTF_CHANGES
template <class Finder, class Reader>
void enumerateFreeObjects(Finder& finder, const Reader& reader)
{
for (void* nextObject = list_; nextObject; nextObject = *reader(reinterpret_cast<void**>(nextObject)))
finder.visit(nextObject);
}
#endif
};
//-------------------------------------------------------------------
// Data kept per thread
//-------------------------------------------------------------------
class TCMalloc_ThreadCache {
private:
typedef TCMalloc_ThreadCache_FreeList FreeList;
#if COMPILER(MSVC)
typedef DWORD ThreadIdentifier;
#else
typedef pthread_t ThreadIdentifier;
#endif
size_t size_; // Combined size of data
ThreadIdentifier tid_; // Which thread owns it
bool in_setspecific_; // Called pthread_setspecific?
FreeList list_[kNumClasses]; // Array indexed by size-class
// We sample allocations, biased by the size of the allocation
uint32_t rnd_; // Cheap random number generator
size_t bytes_until_sample_; // Bytes until we sample next
// Allocate a new heap. REQUIRES: pageheap_lock is held.
static inline TCMalloc_ThreadCache* NewHeap(ThreadIdentifier tid);
// Use only as pthread thread-specific destructor function.
static void DestroyThreadCache(void* ptr);
public:
// All ThreadCache objects are kept in a linked list (for stats collection)
TCMalloc_ThreadCache* next_;
TCMalloc_ThreadCache* prev_;
void Init(ThreadIdentifier tid);
void Cleanup();
// Accessors (mostly just for printing stats)
int freelist_length(size_t cl) const { return list_[cl].length(); }
// Total byte size in cache
size_t Size() const { return size_; }
void* Allocate(size_t size);
void Deallocate(void* ptr, size_t size_class);
void FetchFromCentralCache(size_t cl, size_t allocationSize);
void ReleaseToCentralCache(size_t cl, int N);
void Scavenge();
void Print() const;
// Record allocation of "k" bytes. Return true iff allocation
// should be sampled
bool SampleAllocation(size_t k);
// Pick next sampling point
void PickNextSample(size_t k);
static void InitModule();
static void InitTSD();
static TCMalloc_ThreadCache* GetThreadHeap();
static TCMalloc_ThreadCache* GetCache();
static TCMalloc_ThreadCache* GetCacheIfPresent();
static TCMalloc_ThreadCache* CreateCacheIfNecessary();
static void DeleteCache(TCMalloc_ThreadCache* heap);
static void BecomeIdle();
static void RecomputeThreadCacheSize();
#ifdef WTF_CHANGES
template <class Finder, class Reader>
void enumerateFreeObjects(Finder& finder, const Reader& reader)
{
for (unsigned sizeClass = 0; sizeClass < kNumClasses; sizeClass++)
list_[sizeClass].enumerateFreeObjects(finder, reader);
}
#endif
};
//-------------------------------------------------------------------
// Data kept per size-class in central cache
//-------------------------------------------------------------------
class TCMalloc_Central_FreeList {
public:
void Init(size_t cl);
// These methods all do internal locking.
// Insert the specified range into the central freelist. N is the number of
// elements in the range.
void InsertRange(void *start, void *end, int N);
// Returns the actual number of fetched elements into N.
void RemoveRange(void **start, void **end, int *N);
// Returns the number of free objects in cache.
size_t length() {
SpinLockHolder h(&lock_);
return counter_;
}
// Returns the number of free objects in the transfer cache.
int tc_length() {
SpinLockHolder h(&lock_);
return used_slots_ * num_objects_to_move[size_class_];
}
#ifdef WTF_CHANGES
template <class Finder, class Reader>
void enumerateFreeObjects(Finder& finder, const Reader& reader)
{
for (Span* span = &empty_; span && span != &empty_; span = (span->next ? reader(span->next) : 0))
ASSERT(!span->objects);
ASSERT(!nonempty_.objects);
for (Span* span = reader(nonempty_.next); span && span != &nonempty_; span = (span->next ? reader(span->next) : 0)) {
for (void* nextObject = span->objects; nextObject; nextObject = *reader(reinterpret_cast<void**>(nextObject)))
finder.visit(nextObject);
}
}
#endif
private:
// REQUIRES: lock_ is held
// Remove object from cache and return.
// Return NULL if no free entries in cache.
void* FetchFromSpans();
// REQUIRES: lock_ is held
// Remove object from cache and return. Fetches
// from pageheap if cache is empty. Only returns
// NULL on allocation failure.
void* FetchFromSpansSafe();
// REQUIRES: lock_ is held
// Release a linked list of objects to spans.
// May temporarily release lock_.
void ReleaseListToSpans(void *start);
// REQUIRES: lock_ is held
// Release an object to spans.
// May temporarily release lock_.
void ReleaseToSpans(void* object);
// REQUIRES: lock_ is held
// Populate cache by fetching from the page heap.
// May temporarily release lock_.
void Populate();
// REQUIRES: lock is held.
// Tries to make room for a TCEntry. If the cache is full it will try to
// expand it at the cost of some other cache size. Return false if there is
// no space.
bool MakeCacheSpace();
// REQUIRES: lock_ for locked_size_class is held.
// Picks a "random" size class to steal TCEntry slot from. In reality it
// just iterates over the sizeclasses but does so without taking a lock.
// Returns true on success.
// May temporarily lock a "random" size class.
static bool EvictRandomSizeClass(size_t locked_size_class, bool force);
// REQUIRES: lock_ is *not* held.
// Tries to shrink the Cache. If force is true it will relase objects to
// spans if it allows it to shrink the cache. Return false if it failed to
// shrink the cache. Decrements cache_size_ on succeess.
// May temporarily take lock_. If it takes lock_, the locked_size_class
// lock is released to the thread from holding two size class locks
// concurrently which could lead to a deadlock.
bool ShrinkCache(int locked_size_class, bool force);
// This lock protects all the data members. cached_entries and cache_size_
// may be looked at without holding the lock.
SpinLock lock_;
// We keep linked lists of empty and non-empty spans.
size_t size_class_; // My size class
Span empty_; // Dummy header for list of empty spans
Span nonempty_; // Dummy header for list of non-empty spans
size_t counter_; // Number of free objects in cache entry
// Here we reserve space for TCEntry cache slots. Since one size class can
// end up getting all the TCEntries quota in the system we just preallocate
// sufficient number of entries here.
TCEntry tc_slots_[kNumTransferEntries];
// Number of currently used cached entries in tc_slots_. This variable is
// updated under a lock but can be read without one.
int32_t used_slots_;
// The current number of slots for this size class. This is an
// adaptive value that is increased if there is lots of traffic
// on a given size class.
int32_t cache_size_;
};
// Pad each CentralCache object to multiple of 64 bytes
class TCMalloc_Central_FreeListPadded : public TCMalloc_Central_FreeList {
private:
char pad_[(64 - (sizeof(TCMalloc_Central_FreeList) % 64)) % 64];
};
//-------------------------------------------------------------------
// Global variables
//-------------------------------------------------------------------
// Central cache -- a collection of free-lists, one per size-class.
// We have a separate lock per free-list to reduce contention.
static TCMalloc_Central_FreeListPadded central_cache[kNumClasses];
// Page-level allocator
static SpinLock pageheap_lock = SPINLOCK_INITIALIZER;
static void* pageheap_memory[(sizeof(TCMalloc_PageHeap) + sizeof(void*) - 1) / sizeof(void*)];
static bool phinited = false;
// Avoid extra level of indirection by making "pageheap" be just an alias
// of pageheap_memory.
typedef union {
void* m_memory;
TCMalloc_PageHeap* m_pageHeap;
} PageHeapUnion;
static inline TCMalloc_PageHeap* getPageHeap()
{
PageHeapUnion u = { &pageheap_memory[0] };
return u.m_pageHeap;
}
#define pageheap getPageHeap()
// If TLS is available, we also store a copy
// of the per-thread object in a __thread variable
// since __thread variables are faster to read
// than pthread_getspecific(). We still need
// pthread_setspecific() because __thread
// variables provide no way to run cleanup
// code when a thread is destroyed.
#ifdef HAVE_TLS
static __thread TCMalloc_ThreadCache *threadlocal_heap;
#endif
// Thread-specific key. Initialization here is somewhat tricky
// because some Linux startup code invokes malloc() before it
// is in a good enough state to handle pthread_keycreate().
// Therefore, we use TSD keys only after tsd_inited is set to true.
// Until then, we use a slow path to get the heap object.
static bool tsd_inited = false;
static pthread_key_t heap_key;
#if COMPILER(MSVC)
DWORD tlsIndex = TLS_OUT_OF_INDEXES;
#endif
static ALWAYS_INLINE void setThreadHeap(TCMalloc_ThreadCache* heap)
{
// still do pthread_setspecific when using MSVC fast TLS to
// benefit from the delete callback.
pthread_setspecific(heap_key, heap);
#if COMPILER(MSVC)
TlsSetValue(tlsIndex, heap);
#endif
}
// Allocator for thread heaps
static PageHeapAllocator<TCMalloc_ThreadCache> threadheap_allocator;
// Linked list of heap objects. Protected by pageheap_lock.
static TCMalloc_ThreadCache* thread_heaps = NULL;
static int thread_heap_count = 0;
// Overall thread cache size. Protected by pageheap_lock.
static size_t overall_thread_cache_size = kDefaultOverallThreadCacheSize;
// Global per-thread cache size. Writes are protected by
// pageheap_lock. Reads are done without any locking, which should be
// fine as long as size_t can be written atomically and we don't place
// invariants between this variable and other pieces of state.
static volatile size_t per_thread_cache_size = kMaxThreadCacheSize;
//-------------------------------------------------------------------
// Central cache implementation
//-------------------------------------------------------------------
void TCMalloc_Central_FreeList::Init(size_t cl) {
lock_.Init();
size_class_ = cl;
DLL_Init(&empty_);
DLL_Init(&nonempty_);
counter_ = 0;
cache_size_ = 1;
used_slots_ = 0;
ASSERT(cache_size_ <= kNumTransferEntries);
}
void TCMalloc_Central_FreeList::ReleaseListToSpans(void* start) {
while (start) {
void *next = SLL_Next(start);
ReleaseToSpans(start);
start = next;
}
}
ALWAYS_INLINE void TCMalloc_Central_FreeList::ReleaseToSpans(void* object) {
const PageID p = reinterpret_cast<uintptr_t>(object) >> kPageShift;
Span* span = pageheap->GetDescriptor(p);
ASSERT(span != NULL);
ASSERT(span->refcount > 0);
// If span is empty, move it to non-empty list
if (span->objects == NULL) {
DLL_Remove(span);
DLL_Prepend(&nonempty_, span);
Event(span, 'N', 0);
}
// The following check is expensive, so it is disabled by default
if (false) {
// Check that object does not occur in list
int got = 0;
for (void* p = span->objects; p != NULL; p = *((void**) p)) {
ASSERT(p != object);
got++;
}
ASSERT(got + span->refcount ==
(span->length<<kPageShift)/ByteSizeForClass(span->sizeclass));
}
counter_++;
span->refcount--;
if (span->refcount == 0) {
Event(span, '#', 0);
counter_ -= (span->length<<kPageShift) / ByteSizeForClass(span->sizeclass);
DLL_Remove(span);
// Release central list lock while operating on pageheap
lock_.Unlock();
{
SpinLockHolder h(&pageheap_lock);
pageheap->Delete(span);
}
lock_.Lock();
} else {
*(reinterpret_cast<void**>(object)) = span->objects;
span->objects = object;
}
}
ALWAYS_INLINE bool TCMalloc_Central_FreeList::EvictRandomSizeClass(
size_t locked_size_class, bool force) {
static int race_counter = 0;
int t = race_counter++; // Updated without a lock, but who cares.
if (t >= static_cast<int>(kNumClasses)) {
while (t >= static_cast<int>(kNumClasses)) {
t -= kNumClasses;
}
race_counter = t;
}
ASSERT(t >= 0);
ASSERT(t < static_cast<int>(kNumClasses));
if (t == static_cast<int>(locked_size_class)) return false;
return central_cache[t].ShrinkCache(static_cast<int>(locked_size_class), force);
}
bool TCMalloc_Central_FreeList::MakeCacheSpace() {
// Is there room in the cache?
if (used_slots_ < cache_size_) return true;
// Check if we can expand this cache?
if (cache_size_ == kNumTransferEntries) return false;
// Ok, we'll try to grab an entry from some other size class.
if (EvictRandomSizeClass(size_class_, false) ||
EvictRandomSizeClass(size_class_, true)) {
// Succeeded in evicting, we're going to make our cache larger.
cache_size_++;
return true;
}
return false;
}
namespace {
class LockInverter {
private:
SpinLock *held_, *temp_;
public:
inline explicit LockInverter(SpinLock* held, SpinLock *temp)
: held_(held), temp_(temp) { held_->Unlock(); temp_->Lock(); }
inline ~LockInverter() { temp_->Unlock(); held_->Lock(); }
};
}
bool TCMalloc_Central_FreeList::ShrinkCache(int locked_size_class, bool force) {
// Start with a quick check without taking a lock.
if (cache_size_ == 0) return false;
// We don't evict from a full cache unless we are 'forcing'.
if (force == false && used_slots_ == cache_size_) return false;
// Grab lock, but first release the other lock held by this thread. We use
// the lock inverter to ensure that we never hold two size class locks
// concurrently. That can create a deadlock because there is no well
// defined nesting order.
LockInverter li(&central_cache[locked_size_class].lock_, &lock_);
ASSERT(used_slots_ <= cache_size_);
ASSERT(0 <= cache_size_);
if (cache_size_ == 0) return false;
if (used_slots_ == cache_size_) {
if (force == false) return false;
// ReleaseListToSpans releases the lock, so we have to make all the
// updates to the central list before calling it.
cache_size_--;
used_slots_--;
ReleaseListToSpans(tc_slots_[used_slots_].head);
return true;
}
cache_size_--;
return true;
}
void TCMalloc_Central_FreeList::InsertRange(void *start, void *end, int N) {
SpinLockHolder h(&lock_);
if (N == num_objects_to_move[size_class_] &&
MakeCacheSpace()) {
int slot = used_slots_++;
ASSERT(slot >=0);
ASSERT(slot < kNumTransferEntries);
TCEntry *entry = &tc_slots_[slot];
entry->head = start;
entry->tail = end;
return;
}
ReleaseListToSpans(start);
}
void TCMalloc_Central_FreeList::RemoveRange(void **start, void **end, int *N) {
int num = *N;
ASSERT(num > 0);
SpinLockHolder h(&lock_);
if (num == num_objects_to_move[size_class_] && used_slots_ > 0) {
int slot = --used_slots_;
ASSERT(slot >= 0);
TCEntry *entry = &tc_slots_[slot];
*start = entry->head;
*end = entry->tail;
return;
}
// TODO: Prefetch multiple TCEntries?
void *tail = FetchFromSpansSafe();
if (!tail) {
// We are completely out of memory.
*start = *end = NULL;
*N = 0;
return;
}
SLL_SetNext(tail, NULL);
void *head = tail;
int count = 1;
while (count < num) {
void *t = FetchFromSpans();
if (!t) break;
SLL_Push(&head, t);
count++;
}
*start = head;
*end = tail;
*N = count;
}
void* TCMalloc_Central_FreeList::FetchFromSpansSafe() {
void *t = FetchFromSpans();
if (!t) {
Populate();
t = FetchFromSpans();
}
return t;
}
void* TCMalloc_Central_FreeList::FetchFromSpans() {
if (DLL_IsEmpty(&nonempty_)) return NULL;
Span* span = nonempty_.next;
ASSERT(span->objects != NULL);
span->refcount++;
void* result = span->objects;
span->objects = *(reinterpret_cast<void**>(result));
if (span->objects == NULL) {
// Move to empty list
DLL_Remove(span);
DLL_Prepend(&empty_, span);
Event(span, 'E', 0);
}
counter_--;
return result;
}
// Fetch memory from the system and add to the central cache freelist.
ALWAYS_INLINE void TCMalloc_Central_FreeList::Populate() {
// Release central list lock while operating on pageheap
lock_.Unlock();
const size_t npages = class_to_pages[size_class_];
Span* span;
{
SpinLockHolder h(&pageheap_lock);
span = pageheap->New(npages);
if (span) pageheap->RegisterSizeClass(span, size_class_);
}
if (span == NULL) {
MESSAGE("allocation failed: %d\n", errno);
lock_.Lock();
return;
}
ASSERT(span->length == npages);
// Cache sizeclass info eagerly. Locking is not necessary.
// (Instead of being eager, we could just replace any stale info
// about this span, but that seems to be no better in practice.)
for (size_t i = 0; i < npages; i++) {
pageheap->CacheSizeClass(span->start + i, size_class_);
}
// Split the block into pieces and add to the free-list
// TODO: coloring of objects to avoid cache conflicts?
void** tail = &span->objects;
char* ptr = reinterpret_cast<char*>(span->start << kPageShift);
char* limit = ptr + (npages << kPageShift);
const size_t size = ByteSizeForClass(size_class_);
int num = 0;
char* nptr;
while ((nptr = ptr + size) <= limit) {
*tail = ptr;
tail = reinterpret_cast<void**>(ptr);
ptr = nptr;
num++;
}
ASSERT(ptr <= limit);
*tail = NULL;
span->refcount = 0; // No sub-object in use yet
// Add span to list of non-empty spans
lock_.Lock();
DLL_Prepend(&nonempty_, span);
counter_ += num;
}
//-------------------------------------------------------------------
// TCMalloc_ThreadCache implementation
//-------------------------------------------------------------------
inline bool TCMalloc_ThreadCache::SampleAllocation(size_t k) {
if (bytes_until_sample_ < k) {
PickNextSample(k);
return true;
} else {
bytes_until_sample_ -= k;
return false;
}
}
void TCMalloc_ThreadCache::Init(ThreadIdentifier tid) {
size_ = 0;
next_ = NULL;
prev_ = NULL;
tid_ = tid;
in_setspecific_ = false;
for (size_t cl = 0; cl < kNumClasses; ++cl) {
list_[cl].Init();
}
// Initialize RNG -- run it for a bit to get to good values
bytes_until_sample_ = 0;
rnd_ = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(this));
for (int i = 0; i < 100; i++) {
PickNextSample(static_cast<size_t>(FLAGS_tcmalloc_sample_parameter * 2));
}
}
void TCMalloc_ThreadCache::Cleanup() {
// Put unused memory back into central cache
for (size_t cl = 0; cl < kNumClasses; ++cl) {
if (list_[cl].length() > 0) {
ReleaseToCentralCache(cl, list_[cl].length());
}
}
}
ALWAYS_INLINE void* TCMalloc_ThreadCache::Allocate(size_t size) {
ASSERT(size <= kMaxSize);
const size_t cl = SizeClass(size);
FreeList* list = &list_[cl];
size_t allocationSize = ByteSizeForClass(cl);
if (list->empty()) {
FetchFromCentralCache(cl, allocationSize);
if (list->empty()) return NULL;
}
size_ -= allocationSize;
return list->Pop();
}
inline void TCMalloc_ThreadCache::Deallocate(void* ptr, size_t cl) {
size_ += ByteSizeForClass(cl);
FreeList* list = &list_[cl];
list->Push(ptr);
// If enough data is free, put back into central cache
if (list->length() > kMaxFreeListLength) {
ReleaseToCentralCache(cl, num_objects_to_move[cl]);
}
if (size_ >= per_thread_cache_size) Scavenge();
}
// Remove some objects of class "cl" from central cache and add to thread heap
ALWAYS_INLINE void TCMalloc_ThreadCache::FetchFromCentralCache(size_t cl, size_t allocationSize) {
int fetch_count = num_objects_to_move[cl];
void *start, *end;
central_cache[cl].RemoveRange(&start, &end, &fetch_count);
list_[cl].PushRange(fetch_count, start, end);
size_ += allocationSize * fetch_count;
}
// Remove some objects of class "cl" from thread heap and add to central cache
inline void TCMalloc_ThreadCache::ReleaseToCentralCache(size_t cl, int N) {
ASSERT(N > 0);
FreeList* src = &list_[cl];
if (N > src->length()) N = src->length();
size_ -= N*ByteSizeForClass(cl);
// We return prepackaged chains of the correct size to the central cache.
// TODO: Use the same format internally in the thread caches?
int batch_size = num_objects_to_move[cl];
while (N > batch_size) {
void *tail, *head;
src->PopRange(batch_size, &head, &tail);
central_cache[cl].InsertRange(head, tail, batch_size);
N -= batch_size;
}
void *tail, *head;
src->PopRange(N, &head, &tail);
central_cache[cl].InsertRange(head, tail, N);
}
// Release idle memory to the central cache
inline void TCMalloc_ThreadCache::Scavenge() {
// If the low-water mark for the free list is L, it means we would
// not have had to allocate anything from the central cache even if
// we had reduced the free list size by L. We aim to get closer to
// that situation by dropping L/2 nodes from the free list. This
// may not release much memory, but if so we will call scavenge again
// pretty soon and the low-water marks will be high on that call.
//int64 start = CycleClock::Now();
for (size_t cl = 0; cl < kNumClasses; cl++) {
FreeList* list = &list_[cl];
const int lowmark = list->lowwatermark();
if (lowmark > 0) {
const int drop = (lowmark > 1) ? lowmark/2 : 1;
ReleaseToCentralCache(cl, drop);
}
list->clear_lowwatermark();
}
//int64 finish = CycleClock::Now();
//CycleTimer ct;
//MESSAGE("GC: %.0f ns\n", ct.CyclesToUsec(finish-start)*1000.0);
}
void TCMalloc_ThreadCache::PickNextSample(size_t k) {
// Make next "random" number
// x^32+x^22+x^2+x^1+1 is a primitive polynomial for random numbers
static const uint32_t kPoly = (1 << 22) | (1 << 2) | (1 << 1) | (1 << 0);
uint32_t r = rnd_;
rnd_ = (r << 1) ^ ((static_cast<int32_t>(r) >> 31) & kPoly);
// Next point is "rnd_ % (sample_period)". I.e., average
// increment is "sample_period/2".
const int flag_value = static_cast<int>(FLAGS_tcmalloc_sample_parameter);
static int last_flag_value = -1;
if (flag_value != last_flag_value) {
SpinLockHolder h(&sample_period_lock);
int i;
for (i = 0; i < (static_cast<int>(sizeof(primes_list)/sizeof(primes_list[0])) - 1); i++) {
if (primes_list[i] >= flag_value) {
break;
}
}
sample_period = primes_list[i];
last_flag_value = flag_value;
}
bytes_until_sample_ += rnd_ % sample_period;
if (k > (static_cast<size_t>(-1) >> 2)) {
// If the user has asked for a huge allocation then it is possible
// for the code below to loop infinitely. Just return (note that
// this throws off the sampling accuracy somewhat, but a user who
// is allocating more than 1G of memory at a time can live with a
// minor inaccuracy in profiling of small allocations, and also
// would rather not wait for the loop below to terminate).
return;
}
while (bytes_until_sample_ < k) {
// Increase bytes_until_sample_ by enough average sampling periods
// (sample_period >> 1) to allow us to sample past the current
// allocation.
bytes_until_sample_ += (sample_period >> 1);
}
bytes_until_sample_ -= k;
}
void TCMalloc_ThreadCache::InitModule() {
// There is a slight potential race here because of double-checked
// locking idiom. However, as long as the program does a small
// allocation before switching to multi-threaded mode, we will be
// fine. We increase the chances of doing such a small allocation
// by doing one in the constructor of the module_enter_exit_hook
// object declared below.
SpinLockHolder h(&pageheap_lock);
if (!phinited) {
#ifdef WTF_CHANGES
InitTSD();
#endif
InitSizeClasses();
threadheap_allocator.Init();
span_allocator.Init();
span_allocator.New(); // Reduce cache conflicts
span_allocator.New(); // Reduce cache conflicts
stacktrace_allocator.Init();
DLL_Init(&sampled_objects);
for (size_t i = 0; i < kNumClasses; ++i) {
central_cache[i].Init(i);
}
pageheap->init();
phinited = 1;
#if defined(WTF_CHANGES) && PLATFORM(DARWIN)
FastMallocZone::init();
#endif
}
}
inline TCMalloc_ThreadCache* TCMalloc_ThreadCache::NewHeap(ThreadIdentifier tid) {
// Create the heap and add it to the linked list
TCMalloc_ThreadCache *heap = threadheap_allocator.New();
heap->Init(tid);
heap->next_ = thread_heaps;
heap->prev_ = NULL;
if (thread_heaps != NULL) thread_heaps->prev_ = heap;
thread_heaps = heap;
thread_heap_count++;
RecomputeThreadCacheSize();
return heap;
}
inline TCMalloc_ThreadCache* TCMalloc_ThreadCache::GetThreadHeap() {
#ifdef HAVE_TLS
// __thread is faster, but only when the kernel supports it
if (KernelSupportsTLS())
return threadlocal_heap;
#elif COMPILER(MSVC)
return static_cast<TCMalloc_ThreadCache*>(TlsGetValue(tlsIndex));
#else
return static_cast<TCMalloc_ThreadCache*>(pthread_getspecific(heap_key));
#endif
}
inline TCMalloc_ThreadCache* TCMalloc_ThreadCache::GetCache() {
TCMalloc_ThreadCache* ptr = NULL;
if (!tsd_inited) {
InitModule();
} else {
ptr = GetThreadHeap();
}
if (ptr == NULL) ptr = CreateCacheIfNecessary();
return ptr;
}
// In deletion paths, we do not try to create a thread-cache. This is
// because we may be in the thread destruction code and may have
// already cleaned up the cache for this thread.
inline TCMalloc_ThreadCache* TCMalloc_ThreadCache::GetCacheIfPresent() {
if (!tsd_inited) return NULL;
void* const p = GetThreadHeap();
return reinterpret_cast<TCMalloc_ThreadCache*>(p);
}
void TCMalloc_ThreadCache::InitTSD() {
ASSERT(!tsd_inited);
pthread_key_create(&heap_key, DestroyThreadCache);
#if COMPILER(MSVC)
tlsIndex = TlsAlloc();
#endif
tsd_inited = true;
#if !COMPILER(MSVC)
// We may have used a fake pthread_t for the main thread. Fix it.
pthread_t zero;
memset(&zero, 0, sizeof(zero));
#endif
#ifndef WTF_CHANGES
SpinLockHolder h(&pageheap_lock);
#else
ASSERT(pageheap_lock.IsHeld());
#endif
for (TCMalloc_ThreadCache* h = thread_heaps; h != NULL; h = h->next_) {
#if COMPILER(MSVC)
if (h->tid_ == 0) {
h->tid_ = GetCurrentThreadId();
}
#else
if (pthread_equal(h->tid_, zero)) {
h->tid_ = pthread_self();
}
#endif
}
}
TCMalloc_ThreadCache* TCMalloc_ThreadCache::CreateCacheIfNecessary() {
// Initialize per-thread data if necessary
TCMalloc_ThreadCache* heap = NULL;
{
SpinLockHolder h(&pageheap_lock);
#if COMPILER(MSVC)
DWORD me;
if (!tsd_inited) {
me = 0;
} else {
me = GetCurrentThreadId();
}
#else
// Early on in glibc's life, we cannot even call pthread_self()
pthread_t me;
if (!tsd_inited) {
memset(&me, 0, sizeof(me));
} else {
me = pthread_self();
}
#endif
// This may be a recursive malloc call from pthread_setspecific()
// In that case, the heap for this thread has already been created
// and added to the linked list. So we search for that first.
for (TCMalloc_ThreadCache* h = thread_heaps; h != NULL; h = h->next_) {
#if COMPILER(MSVC)
if (h->tid_ == me) {
#else
if (pthread_equal(h->tid_, me)) {
#endif
heap = h;
break;
}
}
if (heap == NULL) heap = NewHeap(me);
}
// We call pthread_setspecific() outside the lock because it may
// call malloc() recursively. The recursive call will never get
// here again because it will find the already allocated heap in the
// linked list of heaps.
if (!heap->in_setspecific_ && tsd_inited) {
heap->in_setspecific_ = true;
setThreadHeap(heap);
}
return heap;
}
void TCMalloc_ThreadCache::BecomeIdle() {
if (!tsd_inited) return; // No caches yet
TCMalloc_ThreadCache* heap = GetThreadHeap();
if (heap == NULL) return; // No thread cache to remove
if (heap->in_setspecific_) return; // Do not disturb the active caller
heap->in_setspecific_ = true;
pthread_setspecific(heap_key, NULL);
#ifdef HAVE_TLS
// Also update the copy in __thread
threadlocal_heap = NULL;
#endif
heap->in_setspecific_ = false;
if (GetThreadHeap() == heap) {
// Somehow heap got reinstated by a recursive call to malloc
// from pthread_setspecific. We give up in this case.
return;
}
// We can now get rid of the heap
DeleteCache(heap);
}
void TCMalloc_ThreadCache::DestroyThreadCache(void* ptr) {
// Note that "ptr" cannot be NULL since pthread promises not
// to invoke the destructor on NULL values, but for safety,
// we check anyway.
if (ptr == NULL) return;
#ifdef HAVE_TLS
// Prevent fast path of GetThreadHeap() from returning heap.
threadlocal_heap = NULL;
#endif
DeleteCache(reinterpret_cast<TCMalloc_ThreadCache*>(ptr));
}
void TCMalloc_ThreadCache::DeleteCache(TCMalloc_ThreadCache* heap) {
// Remove all memory from heap
heap->Cleanup();
// Remove from linked list
SpinLockHolder h(&pageheap_lock);
if (heap->next_ != NULL) heap->next_->prev_ = heap->prev_;
if (heap->prev_ != NULL) heap->prev_->next_ = heap->next_;
if (thread_heaps == heap) thread_heaps = heap->next_;
thread_heap_count--;
RecomputeThreadCacheSize();
threadheap_allocator.Delete(heap);
}
void TCMalloc_ThreadCache::RecomputeThreadCacheSize() {
// Divide available space across threads
int n = thread_heap_count > 0 ? thread_heap_count : 1;
size_t space = overall_thread_cache_size / n;
// Limit to allowed range
if (space < kMinThreadCacheSize) space = kMinThreadCacheSize;
if (space > kMaxThreadCacheSize) space = kMaxThreadCacheSize;
per_thread_cache_size = space;
}
void TCMalloc_ThreadCache::Print() const {
for (size_t cl = 0; cl < kNumClasses; ++cl) {
MESSAGE(" %5" PRIuS " : %4d len; %4d lo\n",
ByteSizeForClass(cl),
list_[cl].length(),
list_[cl].lowwatermark());
}
}
// Extract interesting stats
struct TCMallocStats {
uint64_t system_bytes; // Bytes alloced from system
uint64_t thread_bytes; // Bytes in thread caches
uint64_t central_bytes; // Bytes in central cache
uint64_t transfer_bytes; // Bytes in central transfer cache
uint64_t pageheap_bytes; // Bytes in page heap
uint64_t metadata_bytes; // Bytes alloced for metadata
};
#ifndef WTF_CHANGES
// Get stats into "r". Also get per-size-class counts if class_count != NULL
static void ExtractStats(TCMallocStats* r, uint64_t* class_count) {
r->central_bytes = 0;
r->transfer_bytes = 0;
for (int cl = 0; cl < kNumClasses; ++cl) {
const int length = central_cache[cl].length();
const int tc_length = central_cache[cl].tc_length();
r->central_bytes += static_cast<uint64_t>(ByteSizeForClass(cl)) * length;
r->transfer_bytes +=
static_cast<uint64_t>(ByteSizeForClass(cl)) * tc_length;
if (class_count) class_count[cl] = length + tc_length;
}
// Add stats from per-thread heaps
r->thread_bytes = 0;
{ // scope
SpinLockHolder h(&pageheap_lock);
for (TCMalloc_ThreadCache* h = thread_heaps; h != NULL; h = h->next_) {
r->thread_bytes += h->Size();
if (class_count) {
for (size_t cl = 0; cl < kNumClasses; ++cl) {
class_count[cl] += h->freelist_length(cl);
}
}
}
}
{ //scope
SpinLockHolder h(&pageheap_lock);
r->system_bytes = pageheap->SystemBytes();
r->metadata_bytes = metadata_system_bytes;
r->pageheap_bytes = pageheap->FreeBytes();
}
}
#endif
#ifndef WTF_CHANGES
// WRITE stats to "out"
static void DumpStats(TCMalloc_Printer* out, int level) {
TCMallocStats stats;
uint64_t class_count[kNumClasses];
ExtractStats(&stats, (level >= 2 ? class_count : NULL));
if (level >= 2) {
out->printf("------------------------------------------------\n");
uint64_t cumulative = 0;
for (int cl = 0; cl < kNumClasses; ++cl) {
if (class_count[cl] > 0) {
uint64_t class_bytes = class_count[cl] * ByteSizeForClass(cl);
cumulative += class_bytes;
out->printf("class %3d [ %8" PRIuS " bytes ] : "
"%8" PRIu64 " objs; %5.1f MB; %5.1f cum MB\n",
cl, ByteSizeForClass(cl),
class_count[cl],
class_bytes / 1048576.0,
cumulative / 1048576.0);
}
}
SpinLockHolder h(&pageheap_lock);
pageheap->Dump(out);
}
const uint64_t bytes_in_use = stats.system_bytes
- stats.pageheap_bytes
- stats.central_bytes
- stats.transfer_bytes
- stats.thread_bytes;
out->printf("------------------------------------------------\n"
"MALLOC: %12" PRIu64 " Heap size\n"
"MALLOC: %12" PRIu64 " Bytes in use by application\n"
"MALLOC: %12" PRIu64 " Bytes free in page heap\n"
"MALLOC: %12" PRIu64 " Bytes free in central cache\n"
"MALLOC: %12" PRIu64 " Bytes free in transfer cache\n"
"MALLOC: %12" PRIu64 " Bytes free in thread caches\n"
"MALLOC: %12" PRIu64 " Spans in use\n"
"MALLOC: %12" PRIu64 " Thread heaps in use\n"
"MALLOC: %12" PRIu64 " Metadata allocated\n"
"------------------------------------------------\n",
stats.system_bytes,
bytes_in_use,
stats.pageheap_bytes,
stats.central_bytes,
stats.transfer_bytes,
stats.thread_bytes,
uint64_t(span_allocator.inuse()),
uint64_t(threadheap_allocator.inuse()),
stats.metadata_bytes);
}
static void PrintStats(int level) {
const int kBufferSize = 16 << 10;
char* buffer = new char[kBufferSize];
TCMalloc_Printer printer(buffer, kBufferSize);
DumpStats(&printer, level);
write(STDERR_FILENO, buffer, strlen(buffer));
delete[] buffer;
}
static void** DumpStackTraces() {
// Count how much space we need
int needed_slots = 0;
{
SpinLockHolder h(&pageheap_lock);
for (Span* s = sampled_objects.next; s != &sampled_objects; s = s->next) {
StackTrace* stack = reinterpret_cast<StackTrace*>(s->objects);
needed_slots += 3 + stack->depth;
}
needed_slots += 100; // Slop in case sample grows
needed_slots += needed_slots/8; // An extra 12.5% slop
}
void** result = new void*[needed_slots];
if (result == NULL) {
MESSAGE("tcmalloc: could not allocate %d slots for stack traces\n",
needed_slots);
return NULL;
}
SpinLockHolder h(&pageheap_lock);
int used_slots = 0;
for (Span* s = sampled_objects.next; s != &sampled_objects; s = s->next) {
ASSERT(used_slots < needed_slots); // Need to leave room for terminator
StackTrace* stack = reinterpret_cast<StackTrace*>(s->objects);
if (used_slots + 3 + stack->depth >= needed_slots) {
// No more room
break;
}
result[used_slots+0] = reinterpret_cast<void*>(static_cast<uintptr_t>(1));
result[used_slots+1] = reinterpret_cast<void*>(stack->size);
result[used_slots+2] = reinterpret_cast<void*>(stack->depth);
for (int d = 0; d < stack->depth; d++) {
result[used_slots+3+d] = stack->stack[d];
}
used_slots += 3 + stack->depth;
}
result[used_slots] = reinterpret_cast<void*>(static_cast<uintptr_t>(0));
return result;
}
#endif
#ifndef WTF_CHANGES
// TCMalloc's support for extra malloc interfaces
class TCMallocImplementation : public MallocExtension {
public:
virtual void GetStats(char* buffer, int buffer_length) {
ASSERT(buffer_length > 0);
TCMalloc_Printer printer(buffer, buffer_length);
// Print level one stats unless lots of space is available
if (buffer_length < 10000) {
DumpStats(&printer, 1);
} else {
DumpStats(&printer, 2);
}
}
virtual void** ReadStackTraces() {
return DumpStackTraces();
}
virtual bool GetNumericProperty(const char* name, size_t* value) {
ASSERT(name != NULL);
if (strcmp(name, "generic.current_allocated_bytes") == 0) {
TCMallocStats stats;
ExtractStats(&stats, NULL);
*value = stats.system_bytes
- stats.thread_bytes
- stats.central_bytes
- stats.pageheap_bytes;
return true;
}
if (strcmp(name, "generic.heap_size") == 0) {
TCMallocStats stats;
ExtractStats(&stats, NULL);
*value = stats.system_bytes;
return true;
}
if (strcmp(name, "tcmalloc.slack_bytes") == 0) {
// We assume that bytes in the page heap are not fragmented too
// badly, and are therefore available for allocation.
SpinLockHolder l(&pageheap_lock);
*value = pageheap->FreeBytes();
return true;
}
if (strcmp(name, "tcmalloc.max_total_thread_cache_bytes") == 0) {
SpinLockHolder l(&pageheap_lock);
*value = overall_thread_cache_size;
return true;
}
if (strcmp(name, "tcmalloc.current_total_thread_cache_bytes") == 0) {
TCMallocStats stats;
ExtractStats(&stats, NULL);
*value = stats.thread_bytes;
return true;
}
return false;
}
virtual bool SetNumericProperty(const char* name, size_t value) {
ASSERT(name != NULL);
if (strcmp(name, "tcmalloc.max_total_thread_cache_bytes") == 0) {
// Clip the value to a reasonable range
if (value < kMinThreadCacheSize) value = kMinThreadCacheSize;
if (value > (1<<30)) value = (1<<30); // Limit to 1GB
SpinLockHolder l(&pageheap_lock);
overall_thread_cache_size = static_cast<size_t>(value);
TCMalloc_ThreadCache::RecomputeThreadCacheSize();
return true;
}
return false;
}
virtual void MarkThreadIdle() {
TCMalloc_ThreadCache::BecomeIdle();
}
virtual void ReleaseFreeMemory() {
SpinLockHolder h(&pageheap_lock);
pageheap->ReleaseFreePages();
}
};
#endif
// The constructor allocates an object to ensure that initialization
// runs before main(), and therefore we do not have a chance to become
// multi-threaded before initialization. We also create the TSD key
// here. Presumably by the time this constructor runs, glibc is in
// good enough shape to handle pthread_key_create().
//
// The constructor also takes the opportunity to tell STL to use
// tcmalloc. We want to do this early, before construct time, so
// all user STL allocations go through tcmalloc (which works really
// well for STL).
//
// The destructor prints stats when the program exits.
class TCMallocGuard {
public:
TCMallocGuard() {
#ifdef HAVE_TLS // this is true if the cc/ld/libc combo support TLS
// Check whether the kernel also supports TLS (needs to happen at runtime)
CheckIfKernelSupportsTLS();
#endif
#ifndef WTF_CHANGES
#ifdef WIN32 // patch the windows VirtualAlloc, etc.
PatchWindowsFunctions(); // defined in windows/patch_functions.cc
#endif
#endif
free(malloc(1));
TCMalloc_ThreadCache::InitTSD();
free(malloc(1));
#ifndef WTF_CHANGES
MallocExtension::Register(new TCMallocImplementation);
#endif
}
#ifndef WTF_CHANGES
~TCMallocGuard() {
const char* env = getenv("MALLOCSTATS");
if (env != NULL) {
int level = atoi(env);
if (level < 1) level = 1;
PrintStats(level);
}
#ifdef WIN32
UnpatchWindowsFunctions();
#endif
}
#endif
};
#ifndef WTF_CHANGES
static TCMallocGuard module_enter_exit_hook;
#endif
//-------------------------------------------------------------------
// Helpers for the exported routines below
//-------------------------------------------------------------------
#ifndef WTF_CHANGES
static Span* DoSampledAllocation(size_t size) {
// Grab the stack trace outside the heap lock
StackTrace tmp;
tmp.depth = GetStackTrace(tmp.stack, kMaxStackDepth, 1);
tmp.size = size;
SpinLockHolder h(&pageheap_lock);
// Allocate span
Span *span = pageheap->New(pages(size == 0 ? 1 : size));
if (span == NULL) {
return NULL;
}
// Allocate stack trace
StackTrace *stack = stacktrace_allocator.New();
if (stack == NULL) {
// Sampling failed because of lack of memory
return span;
}
*stack = tmp;
span->sample = 1;
span->objects = stack;
DLL_Prepend(&sampled_objects, span);
return span;
}
#endif
static inline bool CheckCachedSizeClass(void *ptr) {
PageID p = reinterpret_cast<uintptr_t>(ptr) >> kPageShift;
size_t cached_value = pageheap->GetSizeClassIfCached(p);
return cached_value == 0 ||
cached_value == pageheap->GetDescriptor(p)->sizeclass;
}
static inline void* CheckedMallocResult(void *result)
{
ASSERT(result == 0 || CheckCachedSizeClass(result));
return result;
}
static inline void* SpanToMallocResult(Span *span) {
pageheap->CacheSizeClass(span->start, 0);
return
CheckedMallocResult(reinterpret_cast<void*>(span->start << kPageShift));
}
static ALWAYS_INLINE void* do_malloc(size_t size) {
void* ret = NULL;
#ifdef WTF_CHANGES
ASSERT(!isForbidden());
#endif
// The following call forces module initialization
TCMalloc_ThreadCache* heap = TCMalloc_ThreadCache::GetCache();
#ifndef WTF_CHANGES
if ((FLAGS_tcmalloc_sample_parameter > 0) && heap->SampleAllocation(size)) {
Span* span = DoSampledAllocation(size);
if (span != NULL) {
ret = SpanToMallocResult(span);
}
} else
#endif
if (size > kMaxSize) {
// Use page-level allocator
SpinLockHolder h(&pageheap_lock);
Span* span = pageheap->New(pages(size));
if (span != NULL) {
ret = SpanToMallocResult(span);
}
} else {
// The common case, and also the simplest. This just pops the
// size-appropriate freelist, afer replenishing it if it's empty.
ret = CheckedMallocResult(heap->Allocate(size));
}
if (ret == NULL) errno = ENOMEM;
return ret;
}
static ALWAYS_INLINE void do_free(void* ptr) {
if (ptr == NULL) return;
ASSERT(pageheap != NULL); // Should not call free() before malloc()
const PageID p = reinterpret_cast<uintptr_t>(ptr) >> kPageShift;
Span* span = NULL;
size_t cl = pageheap->GetSizeClassIfCached(p);
if (cl == 0) {
span = pageheap->GetDescriptor(p);
cl = span->sizeclass;
pageheap->CacheSizeClass(p, cl);
}
if (cl != 0) {
ASSERT(!pageheap->GetDescriptor(p)->sample);
TCMalloc_ThreadCache* heap = TCMalloc_ThreadCache::GetCacheIfPresent();
if (heap != NULL) {
heap->Deallocate(ptr, cl);
} else {
// Delete directly into central cache
SLL_SetNext(ptr, NULL);
central_cache[cl].InsertRange(ptr, ptr, 1);
}
} else {
SpinLockHolder h(&pageheap_lock);
ASSERT(reinterpret_cast<uintptr_t>(ptr) % kPageSize == 0);
ASSERT(span != NULL && span->start == p);
if (span->sample) {
DLL_Remove(span);
stacktrace_allocator.Delete(reinterpret_cast<StackTrace*>(span->objects));
span->objects = NULL;
}
pageheap->Delete(span);
}
}
#ifndef WTF_CHANGES
// For use by exported routines below that want specific alignments
//
// Note: this code can be slow, and can significantly fragment memory.
// The expectation is that memalign/posix_memalign/valloc/pvalloc will
// not be invoked very often. This requirement simplifies our
// implementation and allows us to tune for expected allocation
// patterns.
static void* do_memalign(size_t align, size_t size) {
ASSERT((align & (align - 1)) == 0);
ASSERT(align > 0);
if (pageheap == NULL) TCMalloc_ThreadCache::InitModule();
// Allocate at least one byte to avoid boundary conditions below
if (size == 0) size = 1;
if (size <= kMaxSize && align < kPageSize) {
// Search through acceptable size classes looking for one with
// enough alignment. This depends on the fact that
// InitSizeClasses() currently produces several size classes that
// are aligned at powers of two. We will waste time and space if
// we miss in the size class array, but that is deemed acceptable
// since memalign() should be used rarely.
size_t cl = SizeClass(size);
while (cl < kNumClasses && ((class_to_size[cl] & (align - 1)) != 0)) {
cl++;
}
if (cl < kNumClasses) {
TCMalloc_ThreadCache* heap = TCMalloc_ThreadCache::GetCache();
return CheckedMallocResult(heap->Allocate(class_to_size[cl]));
}
}
// We will allocate directly from the page heap
SpinLockHolder h(&pageheap_lock);
if (align <= kPageSize) {
// Any page-level allocation will be fine
// TODO: We could put the rest of this page in the appropriate
// TODO: cache but it does not seem worth it.
Span* span = pageheap->New(pages(size));
return span == NULL ? NULL : SpanToMallocResult(span);
}
// Allocate extra pages and carve off an aligned portion
const Length alloc = pages(size + align);
Span* span = pageheap->New(alloc);
if (span == NULL) return NULL;
// Skip starting portion so that we end up aligned
Length skip = 0;
while ((((span->start+skip) << kPageShift) & (align - 1)) != 0) {
skip++;
}
ASSERT(skip < alloc);
if (skip > 0) {
Span* rest = pageheap->Split(span, skip);
pageheap->Delete(span);
span = rest;
}
// Skip trailing portion that we do not need to return
const Length needed = pages(size);
ASSERT(span->length >= needed);
if (span->length > needed) {
Span* trailer = pageheap->Split(span, needed);
pageheap->Delete(trailer);
}
return SpanToMallocResult(span);
}
#endif
// Helpers for use by exported routines below:
#ifndef WTF_CHANGES
static inline void do_malloc_stats() {
PrintStats(1);
}
#endif
static inline int do_mallopt(int, int) {
return 1; // Indicates error
}
#ifdef HAVE_STRUCT_MALLINFO // mallinfo isn't defined on freebsd, for instance
static inline struct mallinfo do_mallinfo() {
TCMallocStats stats;
ExtractStats(&stats, NULL);
// Just some of the fields are filled in.
struct mallinfo info;
memset(&info, 0, sizeof(info));
// Unfortunately, the struct contains "int" field, so some of the
// size values will be truncated.
info.arena = static_cast<int>(stats.system_bytes);
info.fsmblks = static_cast<int>(stats.thread_bytes
+ stats.central_bytes
+ stats.transfer_bytes);
info.fordblks = static_cast<int>(stats.pageheap_bytes);
info.uordblks = static_cast<int>(stats.system_bytes
- stats.thread_bytes
- stats.central_bytes
- stats.transfer_bytes
- stats.pageheap_bytes);
return info;
}
#endif
//-------------------------------------------------------------------
// Exported routines
//-------------------------------------------------------------------
// CAVEAT: The code structure below ensures that MallocHook methods are always
// called from the stack frame of the invoked allocation function.
// heap-checker.cc depends on this to start a stack trace from
// the call to the (de)allocation function.
#ifndef WTF_CHANGES
extern "C"
#endif
void* malloc(size_t size) {
void* result = do_malloc(size);
#ifndef WTF_CHANGES
MallocHook::InvokeNewHook(result, size);
#endif
return result;
}
#ifndef WTF_CHANGES
extern "C"
#endif
void free(void* ptr) {
#ifndef WTF_CHANGES
MallocHook::InvokeDeleteHook(ptr);
#endif
do_free(ptr);
}
#ifndef WTF_CHANGES
extern "C"
#endif
void* calloc(size_t n, size_t elem_size) {
const size_t totalBytes = n * elem_size;
// Protect against overflow
if (n > 1 && elem_size && (totalBytes / elem_size) != n)
return 0;
void* result = do_malloc(totalBytes);
if (result != NULL) {
memset(result, 0, totalBytes);
}
#ifndef WTF_CHANGES
MallocHook::InvokeNewHook(result, totalBytes);
#endif
return result;
}
#ifndef WTF_CHANGES
extern "C"
#endif
void cfree(void* ptr) {
#ifndef WTF_CHANGES
MallocHook::InvokeDeleteHook(ptr);
#endif
do_free(ptr);
}
#ifndef WTF_CHANGES
extern "C"
#endif
void* realloc(void* old_ptr, size_t new_size) {
if (old_ptr == NULL) {
void* result = do_malloc(new_size);
#ifndef WTF_CHANGES
MallocHook::InvokeNewHook(result, new_size);
#endif
return result;
}
if (new_size == 0) {
#ifndef WTF_CHANGES
MallocHook::InvokeDeleteHook(old_ptr);
#endif
free(old_ptr);
return NULL;
}
// Get the size of the old entry
const PageID p = reinterpret_cast<uintptr_t>(old_ptr) >> kPageShift;
size_t cl = pageheap->GetSizeClassIfCached(p);
Span *span = NULL;
size_t old_size;
if (cl == 0) {
span = pageheap->GetDescriptor(p);
cl = span->sizeclass;
pageheap->CacheSizeClass(p, cl);
}
if (cl != 0) {
old_size = ByteSizeForClass(cl);
} else {
ASSERT(span != NULL);
old_size = span->length << kPageShift;
}
// Reallocate if the new size is larger than the old size,
// or if the new size is significantly smaller than the old size.
if ((new_size > old_size) || (AllocationSize(new_size) < old_size)) {
// Need to reallocate
void* new_ptr = do_malloc(new_size);
if (new_ptr == NULL) {
return NULL;
}
#ifndef WTF_CHANGES
MallocHook::InvokeNewHook(new_ptr, new_size);
#endif
memcpy(new_ptr, old_ptr, ((old_size < new_size) ? old_size : new_size));
#ifndef WTF_CHANGES
MallocHook::InvokeDeleteHook(old_ptr);
#endif
// We could use a variant of do_free() that leverages the fact
// that we already know the sizeclass of old_ptr. The benefit
// would be small, so don't bother.
do_free(old_ptr);
return new_ptr;
} else {
return old_ptr;
}
}
#ifndef WTF_CHANGES
static SpinLock set_new_handler_lock = SPINLOCK_INITIALIZER;
static inline void* cpp_alloc(size_t size, bool nothrow) {
for (;;) {
void* p = do_malloc(size);
#ifdef PREANSINEW
return p;
#else
if (p == NULL) { // allocation failed
// Get the current new handler. NB: this function is not
// thread-safe. We make a feeble stab at making it so here, but
// this lock only protects against tcmalloc interfering with
// itself, not with other libraries calling set_new_handler.
std::new_handler nh;
{
SpinLockHolder h(&set_new_handler_lock);
nh = std::set_new_handler(0);
(void) std::set_new_handler(nh);
}
// If no new_handler is established, the allocation failed.
if (!nh) {
if (nothrow) return 0;
throw std::bad_alloc();
}
// Otherwise, try the new_handler. If it returns, retry the
// allocation. If it throws std::bad_alloc, fail the allocation.
// if it throws something else, don't interfere.
try {
(*nh)();
} catch (const std::bad_alloc&) {
if (!nothrow) throw;
return p;
}
} else { // allocation success
return p;
}
#endif
}
}
void* operator new(size_t size) {
void* p = cpp_alloc(size, false);
// We keep this next instruction out of cpp_alloc for a reason: when
// it's in, and new just calls cpp_alloc, the optimizer may fold the
// new call into cpp_alloc, which messes up our whole section-based
// stacktracing (see ATTRIBUTE_SECTION, above). This ensures cpp_alloc
// isn't the last thing this fn calls, and prevents the folding.
MallocHook::InvokeNewHook(p, size);
return p;
}
void* operator new(size_t size, const std::nothrow_t&) __THROW {
void* p = cpp_alloc(size, true);
MallocHook::InvokeNewHook(p, size);
return p;
}
void operator delete(void* p) __THROW {
MallocHook::InvokeDeleteHook(p);
do_free(p);
}
void operator delete(void* p, const std::nothrow_t&) __THROW {
MallocHook::InvokeDeleteHook(p);
do_free(p);
}
void* operator new[](size_t size) {
void* p = cpp_alloc(size, false);
// We keep this next instruction out of cpp_alloc for a reason: when
// it's in, and new just calls cpp_alloc, the optimizer may fold the
// new call into cpp_alloc, which messes up our whole section-based
// stacktracing (see ATTRIBUTE_SECTION, above). This ensures cpp_alloc
// isn't the last thing this fn calls, and prevents the folding.
MallocHook::InvokeNewHook(p, size);
return p;
}
void* operator new[](size_t size, const std::nothrow_t&) __THROW {
void* p = cpp_alloc(size, true);
MallocHook::InvokeNewHook(p, size);
return p;
}
void operator delete[](void* p) __THROW {
MallocHook::InvokeDeleteHook(p);
do_free(p);
}
void operator delete[](void* p, const std::nothrow_t&) __THROW {
MallocHook::InvokeDeleteHook(p);
do_free(p);
}
extern "C" void* memalign(size_t align, size_t size) __THROW {
void* result = do_memalign(align, size);
MallocHook::InvokeNewHook(result, size);
return result;
}
extern "C" int posix_memalign(void** result_ptr, size_t align, size_t size)
__THROW {
if (((align % sizeof(void*)) != 0) ||
((align & (align - 1)) != 0) ||
(align == 0)) {
return EINVAL;
}
void* result = do_memalign(align, size);
MallocHook::InvokeNewHook(result, size);
if (result == NULL) {
return ENOMEM;
} else {
*result_ptr = result;
return 0;
}
}
static size_t pagesize = 0;
extern "C" void* valloc(size_t size) __THROW {
// Allocate page-aligned object of length >= size bytes
if (pagesize == 0) pagesize = getpagesize();
void* result = do_memalign(pagesize, size);
MallocHook::InvokeNewHook(result, size);
return result;
}
extern "C" void* pvalloc(size_t size) __THROW {
// Round up size to a multiple of pagesize
if (pagesize == 0) pagesize = getpagesize();
size = (size + pagesize - 1) & ~(pagesize - 1);
void* result = do_memalign(pagesize, size);
MallocHook::InvokeNewHook(result, size);
return result;
}
extern "C" void malloc_stats(void) {
do_malloc_stats();
}
extern "C" int mallopt(int cmd, int value) {
return do_mallopt(cmd, value);
}
#ifdef HAVE_STRUCT_MALLINFO
extern "C" struct mallinfo mallinfo(void) {
return do_mallinfo();
}
#endif
//-------------------------------------------------------------------
// Some library routines on RedHat 9 allocate memory using malloc()
// and free it using __libc_free() (or vice-versa). Since we provide
// our own implementations of malloc/free, we need to make sure that
// the __libc_XXX variants (defined as part of glibc) also point to
// the same implementations.
//-------------------------------------------------------------------
#if defined(__GLIBC__)
extern "C" {
# if defined(__GNUC__) && !defined(__MACH__) && defined(HAVE___ATTRIBUTE__)
// Potentially faster variants that use the gcc alias extension.
// Mach-O (Darwin) does not support weak aliases, hence the __MACH__ check.
# define ALIAS(x) __attribute__ ((weak, alias (x)))
void* __libc_malloc(size_t size) ALIAS("malloc");
void __libc_free(void* ptr) ALIAS("free");
void* __libc_realloc(void* ptr, size_t size) ALIAS("realloc");
void* __libc_calloc(size_t n, size_t size) ALIAS("calloc");
void __libc_cfree(void* ptr) ALIAS("cfree");
void* __libc_memalign(size_t align, size_t s) ALIAS("memalign");
void* __libc_valloc(size_t size) ALIAS("valloc");
void* __libc_pvalloc(size_t size) ALIAS("pvalloc");
int __posix_memalign(void** r, size_t a, size_t s) ALIAS("posix_memalign");
# undef ALIAS
# else /* not __GNUC__ */
// Portable wrappers
void* __libc_malloc(size_t size) { return malloc(size); }
void __libc_free(void* ptr) { free(ptr); }
void* __libc_realloc(void* ptr, size_t size) { return realloc(ptr, size); }
void* __libc_calloc(size_t n, size_t size) { return calloc(n, size); }
void __libc_cfree(void* ptr) { cfree(ptr); }
void* __libc_memalign(size_t align, size_t s) { return memalign(align, s); }
void* __libc_valloc(size_t size) { return valloc(size); }
void* __libc_pvalloc(size_t size) { return pvalloc(size); }
int __posix_memalign(void** r, size_t a, size_t s) {
return posix_memalign(r, a, s);
}
# endif /* __GNUC__ */
}
#endif /* __GLIBC__ */
// Override __libc_memalign in libc on linux boxes specially.
// They have a bug in libc that causes them to (very rarely) allocate
// with __libc_memalign() yet deallocate with free() and the
// definitions above don't catch it.
// This function is an exception to the rule of calling MallocHook method
// from the stack frame of the allocation function;
// heap-checker handles this special case explicitly.
static void *MemalignOverride(size_t align, size_t size, const void *caller)
__THROW {
void* result = do_memalign(align, size);
MallocHook::InvokeNewHook(result, size);
return result;
}
void *(*__memalign_hook)(size_t, size_t, const void *) = MemalignOverride;
#endif
#if defined(WTF_CHANGES) && PLATFORM(DARWIN)
#include <wtf/HashSet.h>
class FreeObjectFinder {
const RemoteMemoryReader& m_reader;
HashSet<void*> m_freeObjects;
public:
FreeObjectFinder(const RemoteMemoryReader& reader) : m_reader(reader) { }
void visit(void* ptr) { m_freeObjects.add(ptr); }
bool isFreeObject(void* ptr) const { return m_freeObjects.contains(ptr); }
size_t freeObjectCount() const { return m_freeObjects.size(); }
void findFreeObjects(TCMalloc_ThreadCache* threadCache)
{
for (; threadCache; threadCache = (threadCache->next_ ? m_reader(threadCache->next_) : 0))
threadCache->enumerateFreeObjects(*this, m_reader);
}
void findFreeObjects(TCMalloc_Central_FreeListPadded* centralFreeList, size_t numSizes)
{
for (unsigned i = 0; i < numSizes; i++)
centralFreeList[i].enumerateFreeObjects(*this, m_reader);
}
};
class PageMapFreeObjectFinder {
const RemoteMemoryReader& m_reader;
FreeObjectFinder& m_freeObjectFinder;
public:
PageMapFreeObjectFinder(const RemoteMemoryReader& reader, FreeObjectFinder& freeObjectFinder)
: m_reader(reader)
, m_freeObjectFinder(freeObjectFinder)
{ }
int visit(void* ptr) const
{
if (!ptr)
return 1;
Span* span = m_reader(reinterpret_cast<Span*>(ptr));
if (span->free) {
void* ptr = reinterpret_cast<void*>(span->start << kPageShift);
m_freeObjectFinder.visit(ptr);
} else if (span->sizeclass) {
// Walk the free list of the small-object span, keeping track of each object seen
for (void* nextObject = span->objects; nextObject; nextObject = *m_reader(reinterpret_cast<void**>(nextObject)))
m_freeObjectFinder.visit(nextObject);
}
return span->length;
}
};
class PageMapMemoryUsageRecorder {
task_t m_task;
void* m_context;
unsigned m_typeMask;
vm_range_recorder_t* m_recorder;
const RemoteMemoryReader& m_reader;
const FreeObjectFinder& m_freeObjectFinder;
mutable HashSet<void*> m_seenPointers;
public:
PageMapMemoryUsageRecorder(task_t task, void* context, unsigned typeMask, vm_range_recorder_t* recorder, const RemoteMemoryReader& reader, const FreeObjectFinder& freeObjectFinder)
: m_task(task)
, m_context(context)
, m_typeMask(typeMask)
, m_recorder(recorder)
, m_reader(reader)
, m_freeObjectFinder(freeObjectFinder)
{ }
int visit(void* ptr) const
{
if (!ptr)
return 1;
Span* span = m_reader(reinterpret_cast<Span*>(ptr));
if (m_seenPointers.contains(ptr))
return span->length;
m_seenPointers.add(ptr);
// Mark the memory used for the Span itself as an administrative region
vm_range_t ptrRange = { reinterpret_cast<vm_address_t>(ptr), sizeof(Span) };
if (m_typeMask & (MALLOC_PTR_REGION_RANGE_TYPE | MALLOC_ADMIN_REGION_RANGE_TYPE))
(*m_recorder)(m_task, m_context, MALLOC_ADMIN_REGION_RANGE_TYPE, &ptrRange, 1);
ptrRange.address = span->start << kPageShift;
ptrRange.size = span->length * kPageSize;
// Mark the memory region the span represents as candidates for containing pointers
if (m_typeMask & (MALLOC_PTR_REGION_RANGE_TYPE | MALLOC_ADMIN_REGION_RANGE_TYPE))
(*m_recorder)(m_task, m_context, MALLOC_PTR_REGION_RANGE_TYPE, &ptrRange, 1);
if (!span->free && (m_typeMask & MALLOC_PTR_IN_USE_RANGE_TYPE)) {
// If it's an allocated large object span, mark it as in use
if (span->sizeclass == 0 && !m_freeObjectFinder.isFreeObject(reinterpret_cast<void*>(ptrRange.address)))
(*m_recorder)(m_task, m_context, MALLOC_PTR_IN_USE_RANGE_TYPE, &ptrRange, 1);
else if (span->sizeclass) {
const size_t byteSize = ByteSizeForClass(span->sizeclass);
unsigned totalObjects = (span->length << kPageShift) / byteSize;
ASSERT(span->refcount <= totalObjects);
char* ptr = reinterpret_cast<char*>(span->start << kPageShift);
// Mark each allocated small object within the span as in use
for (unsigned i = 0; i < totalObjects; i++) {
char* thisObject = ptr + (i * byteSize);
if (m_freeObjectFinder.isFreeObject(thisObject))
continue;
vm_range_t objectRange = { reinterpret_cast<vm_address_t>(thisObject), byteSize };
(*m_recorder)(m_task, m_context, MALLOC_PTR_IN_USE_RANGE_TYPE, &objectRange, 1);
}
}
}
return span->length;
}
};
kern_return_t FastMallocZone::enumerate(task_t task, void* context, unsigned typeMask, vm_address_t zoneAddress, memory_reader_t reader, vm_range_recorder_t recorder)
{
RemoteMemoryReader memoryReader(task, reader);
InitSizeClasses();
FastMallocZone* mzone = memoryReader(reinterpret_cast<FastMallocZone*>(zoneAddress));
TCMalloc_PageHeap* pageHeap = memoryReader(mzone->m_pageHeap);
TCMalloc_ThreadCache** threadHeapsPointer = memoryReader(mzone->m_threadHeaps);
TCMalloc_ThreadCache* threadHeaps = memoryReader(*threadHeapsPointer);
TCMalloc_Central_FreeListPadded* centralCaches = memoryReader(mzone->m_centralCaches, sizeof(TCMalloc_Central_FreeListPadded) * kNumClasses);
FreeObjectFinder finder(memoryReader);
finder.findFreeObjects(threadHeaps);
finder.findFreeObjects(centralCaches, kNumClasses);
TCMalloc_PageHeap::PageMap* pageMap = &pageHeap->pagemap_;
PageMapFreeObjectFinder pageMapFinder(memoryReader, finder);
pageMap->visit(pageMapFinder, memoryReader);
PageMapMemoryUsageRecorder usageRecorder(task, context, typeMask, recorder, memoryReader, finder);
pageMap->visit(usageRecorder, memoryReader);
return 0;
}
size_t FastMallocZone::size(malloc_zone_t*, const void*)
{
return 0;
}
void* FastMallocZone::zoneMalloc(malloc_zone_t*, size_t)
{
return 0;
}
void* FastMallocZone::zoneCalloc(malloc_zone_t*, size_t, size_t)
{
return 0;
}
void FastMallocZone::zoneFree(malloc_zone_t*, void* ptr)
{
// Due to <rdar://problem/5671357> zoneFree may be called by the system free even if the pointer
// is not in this zone. When this happens, the pointer being freed was not allocated by any
// zone so we need to print a useful error for the application developer.
malloc_printf("*** error for object %p: pointer being freed was not allocated\n", ptr);
}
void* FastMallocZone::zoneRealloc(malloc_zone_t*, void*, size_t)
{
return 0;
}
#undef malloc
#undef free
#undef realloc
#undef calloc
extern "C" {
malloc_introspection_t jscore_fastmalloc_introspection = { &FastMallocZone::enumerate, &FastMallocZone::goodSize, &FastMallocZone::check, &FastMallocZone::print,
&FastMallocZone::log, &FastMallocZone::forceLock, &FastMallocZone::forceUnlock, &FastMallocZone::statistics };
}
FastMallocZone::FastMallocZone(TCMalloc_PageHeap* pageHeap, TCMalloc_ThreadCache** threadHeaps, TCMalloc_Central_FreeListPadded* centralCaches)
: m_pageHeap(pageHeap)
, m_threadHeaps(threadHeaps)
, m_centralCaches(centralCaches)
{
memset(&m_zone, 0, sizeof(m_zone));
m_zone.zone_name = "JavaScriptCore FastMalloc";
m_zone.size = &FastMallocZone::size;
m_zone.malloc = &FastMallocZone::zoneMalloc;
m_zone.calloc = &FastMallocZone::zoneCalloc;
m_zone.realloc = &FastMallocZone::zoneRealloc;
m_zone.free = &FastMallocZone::zoneFree;
m_zone.valloc = &FastMallocZone::zoneValloc;
m_zone.destroy = &FastMallocZone::zoneDestroy;
m_zone.introspect = &jscore_fastmalloc_introspection;
malloc_zone_register(&m_zone);
}
void FastMallocZone::init()
{
static FastMallocZone zone(pageheap, &thread_heaps, static_cast<TCMalloc_Central_FreeListPadded*>(central_cache));
}
#endif
#if WTF_CHANGES
} // namespace WTF
#endif
#endif // USE_SYSTEM_MALLOC