| /* |
| * Copyright (C) 2016-2018 Apple 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: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. 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. |
| * |
| * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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. |
| */ |
| |
| #ifndef LargeRange_h |
| #define LargeRange_h |
| |
| #include "BAssert.h" |
| #include "Range.h" |
| |
| namespace bmalloc { |
| |
| class LargeRange : public Range { |
| public: |
| LargeRange() |
| : Range() |
| , m_startPhysicalSize(0) |
| , m_totalPhysicalSize(0) |
| { |
| } |
| |
| LargeRange(const Range& other, size_t startPhysicalSize, size_t totalPhysicalSize) |
| : Range(other) |
| , m_startPhysicalSize(startPhysicalSize) |
| , m_totalPhysicalSize(totalPhysicalSize) |
| { |
| BASSERT(this->size() >= this->totalPhysicalSize()); |
| BASSERT(this->totalPhysicalSize() >= this->startPhysicalSize()); |
| } |
| |
| LargeRange(void* begin, size_t size, size_t startPhysicalSize, size_t totalPhysicalSize) |
| : Range(begin, size) |
| , m_startPhysicalSize(startPhysicalSize) |
| , m_totalPhysicalSize(totalPhysicalSize) |
| { |
| BASSERT(this->size() >= this->totalPhysicalSize()); |
| BASSERT(this->totalPhysicalSize() >= this->startPhysicalSize()); |
| } |
| |
| // Returns a lower bound on physical size at the start of the range. Ranges that |
| // span non-physical fragments use this number to remember the physical size of |
| // the first fragment. |
| size_t startPhysicalSize() const { return m_startPhysicalSize; } |
| void setStartPhysicalSize(size_t startPhysicalSize) { m_startPhysicalSize = startPhysicalSize; } |
| |
| // This is accurate in the sense that if you take a range A and split it N ways |
| // and sum totalPhysicalSize over each of the N splits, you'll end up with A's |
| // totalPhysicalSize. This means if you take a LargeRange out of a LargeMap, split it, |
| // then insert the subsequent two ranges back into the LargeMap, the sum of the |
| // totalPhysicalSize of each LargeRange in the LargeMap will stay constant. This |
| // property is not true of startPhysicalSize. This invariant about totalPhysicalSize |
| // is good enough to get an accurate footprint estimate for memory used in bmalloc. |
| // The reason this is just an estimate is that splitting LargeRanges may lead to this |
| // number being rebalanced in arbitrary ways between the two resulting ranges. This |
| // is why the footprint is just an estimate. In practice, this arbitrary rebalance |
| // doesn't really affect accuracy. |
| size_t totalPhysicalSize() const { return m_totalPhysicalSize; } |
| void setTotalPhysicalSize(size_t totalPhysicalSize) { m_totalPhysicalSize = totalPhysicalSize; } |
| |
| std::pair<LargeRange, LargeRange> split(size_t) const; |
| |
| void setEligible(bool eligible) { m_isEligible = eligible; } |
| bool isEligibile() const { return m_isEligible; } |
| |
| bool operator<(const void* other) const { return begin() < other; } |
| bool operator<(const LargeRange& other) const { return begin() < other.begin(); } |
| |
| private: |
| size_t m_startPhysicalSize; |
| size_t m_totalPhysicalSize; |
| bool m_isEligible { true }; |
| }; |
| |
| inline bool canMerge(const LargeRange& a, const LargeRange& b) |
| { |
| if (!a.isEligibile() || !b.isEligibile()) { |
| // FIXME: We can make this work if we find it's helpful as long as the merged |
| // range is only eligible if a and b are eligible. |
| return false; |
| } |
| |
| if (a.end() == b.begin()) |
| return true; |
| |
| if (b.end() == a.begin()) |
| return true; |
| |
| return false; |
| } |
| |
| inline LargeRange merge(const LargeRange& a, const LargeRange& b) |
| { |
| const LargeRange& left = std::min(a, b); |
| if (left.size() == left.startPhysicalSize()) { |
| return LargeRange( |
| left.begin(), |
| a.size() + b.size(), |
| a.startPhysicalSize() + b.startPhysicalSize(), |
| a.totalPhysicalSize() + b.totalPhysicalSize()); |
| } |
| |
| return LargeRange( |
| left.begin(), |
| a.size() + b.size(), |
| left.startPhysicalSize(), |
| a.totalPhysicalSize() + b.totalPhysicalSize()); |
| } |
| |
| inline std::pair<LargeRange, LargeRange> LargeRange::split(size_t leftSize) const |
| { |
| BASSERT(leftSize <= this->size()); |
| size_t rightSize = this->size() - leftSize; |
| |
| if (leftSize <= startPhysicalSize()) { |
| BASSERT(totalPhysicalSize() >= leftSize); |
| LargeRange left(begin(), leftSize, leftSize, leftSize); |
| LargeRange right(left.end(), rightSize, startPhysicalSize() - leftSize, totalPhysicalSize() - leftSize); |
| return std::make_pair(left, right); |
| } |
| |
| double ratio = static_cast<double>(leftSize) / static_cast<double>(this->size()); |
| size_t leftTotalPhysicalSize = static_cast<size_t>(ratio * totalPhysicalSize()); |
| BASSERT(leftTotalPhysicalSize <= leftSize); |
| leftTotalPhysicalSize = std::max(startPhysicalSize(), leftTotalPhysicalSize); |
| size_t rightTotalPhysicalSize = totalPhysicalSize() - leftTotalPhysicalSize; |
| if (rightTotalPhysicalSize > rightSize) { // This may happen because of rounding. |
| leftTotalPhysicalSize += rightTotalPhysicalSize - rightSize; |
| BASSERT(leftTotalPhysicalSize <= leftSize); |
| rightTotalPhysicalSize = rightSize; |
| } |
| |
| LargeRange left(begin(), leftSize, startPhysicalSize(), leftTotalPhysicalSize); |
| LargeRange right(left.end(), rightSize, 0, rightTotalPhysicalSize); |
| return std::make_pair(left, right); |
| } |
| |
| } // namespace bmalloc |
| |
| #endif // LargeRange_h |