Source/WebCore/platform/graphics/cg/IOSurfacePool.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2013, 2014 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. AND ITS 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 APPLE INC. OR ITS 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.
  */

 #include "config.h"
 #include "IOSurfacePool.h"

 #if HAVE(IOSURFACE)

 #include "DestinationColorSpace.h"
 #include "GraphicsContextCG.h"
 #include <CoreGraphics/CoreGraphics.h>
 #include <wtf/NeverDestroyed.h>
 #include <wtf/text/TextStream.h>

 static const Seconds collectionInterval { 500_ms };
 static const Seconds surfaceAgeBeforeMarkingPurgeable { 2_s };

 #define ENABLE_IOSURFACE_POOL_STATISTICS 0
 #if ENABLE_IOSURFACE_POOL_STATISTICS
 #define DUMP_POOL_STATISTICS(commands) do { ALWAYS_LOG_WITH_STREAM(commands); } while (0);
 #else
 #define DUMP_POOL_STATISTICS(commands) ((void)0)
 #endif

 namespace WebCore {

 IOSurfacePool::IOSurfacePool()
     : m_collectionTimer(RunLoop::main(), this, &IOSurfacePool::collectionTimerFired)
 {
 }

 IOSurfacePool& IOSurfacePool::sharedPool()
 {
     static LazyNeverDestroyed<IOSurfacePool> pool;
     static std::once_flag s_onceFlag;
     std::call_once(s_onceFlag, [] {
         pool.construct();
     });
     return pool;
 }

 Ref<IOSurfacePool> IOSurfacePool::create()
 {
     return adoptRef(*new IOSurfacePool);
 }

 static bool surfaceMatchesParameters(IOSurface& surface, IntSize requestedSize, const DestinationColorSpace& colorSpace, IOSurface::Format format)
 {
     if (format != surface.format())
         return false;
     if (colorSpace != surface.colorSpace())
         return false;
     if (requestedSize != surface.size())
         return false;
     return true;
 }

 void IOSurfacePool::willAddSurface(IOSurface& surface, bool inUse)
 {
     CachedSurfaceDetails& details = m_surfaceDetails.add(&surface, CachedSurfaceDetails()).iterator->value;
     details.resetLastUseTime();

     surface.releaseGraphicsContext();

     size_t surfaceBytes = surface.totalBytes();

     evict(surfaceBytes);

     m_bytesCached += surfaceBytes;
     if (inUse)
         m_inUseBytesCached += surfaceBytes;
 }

 void IOSurfacePool::didRemoveSurface(IOSurface& surface, bool inUse)
 {
     size_t surfaceBytes = surface.totalBytes();
     m_bytesCached -= surfaceBytes;
     if (inUse)
         m_inUseBytesCached -= surfaceBytes;

     m_surfaceDetails.remove(&surface);
 }

 void IOSurfacePool::didUseSurfaceOfSize(IntSize size)
 {
     m_sizesInPruneOrder.remove(m_sizesInPruneOrder.reverseFind(size));
     m_sizesInPruneOrder.append(size);
 }

 std::unique_ptr<IOSurface> IOSurfacePool::takeSurface(IntSize size, const DestinationColorSpace& colorSpace, IOSurface::Format format)
 {
     Locker locker { m_lock };
     CachedSurfaceMap::iterator mapIter = m_cachedSurfaces.find(size);

     if (mapIter == m_cachedSurfaces.end()) {
         DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - failed to find surface matching size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
         return nullptr;
     }

     for (auto surfaceIter = mapIter->value.begin(); surfaceIter != mapIter->value.end(); ++surfaceIter) {
         if (!surfaceMatchesParameters(*surfaceIter->get(), size, colorSpace, format))
             continue;

         auto surface = WTFMove(*surfaceIter);
         mapIter->value.remove(surfaceIter);

         didUseSurfaceOfSize(size);

         if (mapIter->value.isEmpty()) {
             m_cachedSurfaces.remove(mapIter);
             m_sizesInPruneOrder.removeLast();
         }

         didRemoveSurface(*surface, false);

         surface->setVolatile(false);

         DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - taking surface " << surface.get() << " with size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
         return surface;
     }

     // Some of the in-use surfaces may no longer actually be in-use, but we haven't moved them over yet.
     for (auto surfaceIter = m_inUseSurfaces.begin(); surfaceIter != m_inUseSurfaces.end(); ++surfaceIter) {
         if (!surfaceMatchesParameters(*surfaceIter->get(), size, colorSpace, format))
             continue;
         if (surfaceIter->get()->isInUse())
             continue;

         auto surface = WTFMove(*surfaceIter);
         m_inUseSurfaces.remove(surfaceIter);
         didRemoveSurface(*surface, true);

         surface->setVolatile(false);

         DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - taking surface " << surface.get() << " with size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
         return surface;
     }

     DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - failing\n" << poolStatistics());
     return nullptr;
 }

 bool IOSurfacePool::shouldCacheSurface(const IOSurface& surface) const
 {
     if (surface.totalBytes() > m_maximumBytesCached)
         return false;

     // There's no reason to pool empty surfaces; we should never allocate them in the first place.
     // This also covers isZero(), which would cause trouble when used as the key in m_cachedSurfaces.
     if (surface.size().isEmpty())
         return false;

     return true;
 }

 void IOSurfacePool::addSurface(std::unique_ptr<IOSurface>&& surface)
 {
     Locker locker { m_lock };
     if (!shouldCacheSurface(*surface))
         return;

     bool surfaceIsInUse = surface->isInUse();

     willAddSurface(*surface, surfaceIsInUse);

     if (surfaceIsInUse) {
         m_inUseSurfaces.prepend(WTFMove(surface));
         scheduleCollectionTimer();
         DUMP_POOL_STATISTICS(stream << "addSurface - in-use\n" << poolStatistics());
         return;
     }

     insertSurfaceIntoPool(WTFMove(surface));
     DUMP_POOL_STATISTICS(stream << "addSurface\n" << poolStatistics());
 }

 void IOSurfacePool::insertSurfaceIntoPool(std::unique_ptr<IOSurface> surface)
 {
     IntSize surfaceSize = surface->size();
     auto insertedTuple = m_cachedSurfaces.add(surfaceSize, CachedSurfaceQueue());
     insertedTuple.iterator->value.prepend(WTFMove(surface));
     if (!insertedTuple.isNewEntry)
         m_sizesInPruneOrder.remove(m_sizesInPruneOrder.reverseFind(surfaceSize));
     m_sizesInPruneOrder.append(surfaceSize);

     scheduleCollectionTimer();
 }

 void IOSurfacePool::setPoolSize(size_t poolSizeInBytes)
 {
     Locker locker { m_lock };
     m_maximumBytesCached = poolSizeInBytes;
     evict(0);
 }

 void IOSurfacePool::tryEvictInUseSurface()
 {
     if (m_inUseSurfaces.isEmpty())
         return;

     auto surface = m_inUseSurfaces.takeLast();
     didRemoveSurface(*surface, true);
 }

 void IOSurfacePool::tryEvictOldestCachedSurface()
 {
     if (m_cachedSurfaces.isEmpty())
         return;

     if (m_sizesInPruneOrder.isEmpty())
         return;

     CachedSurfaceMap::iterator surfaceQueueIter = m_cachedSurfaces.find(m_sizesInPruneOrder.first());
     ASSERT(!surfaceQueueIter->value.isEmpty());
     auto surface = surfaceQueueIter->value.takeLast();
     didRemoveSurface(*surface, false);

     if (surfaceQueueIter->value.isEmpty()) {
         m_cachedSurfaces.remove(surfaceQueueIter);
         m_sizesInPruneOrder.remove(0);
     }
 }

 void IOSurfacePool::evict(size_t additionalSize)
 {
     DUMP_POOL_STATISTICS(stream << "before evict\n" << poolStatistics());

     if (additionalSize >= m_maximumBytesCached) {
         discardAllSurfacesInternal();
         DUMP_POOL_STATISTICS(stream << "after evict all\n" << poolStatistics());
         return;
     }

     // FIXME: Perhaps purgeable surfaces should count less against the cap?
     // We don't want to end up with a ton of empty (purged) surfaces, though, as that would defeat the purpose of the pool.
     size_t targetSize = m_maximumBytesCached - additionalSize;

     // Interleave eviction of old cached surfaces and more recent in-use surfaces.
     // In-use surfaces are more recently used, but less useful in the pool, as they aren't
     // immediately available when requested.
     while (m_bytesCached > targetSize) {
         tryEvictOldestCachedSurface();

         if (m_inUseBytesCached > maximumInUseBytes || m_bytesCached > targetSize)
             tryEvictInUseSurface();
     }

     while (m_inUseBytesCached > maximumInUseBytes || m_bytesCached > targetSize)
         tryEvictInUseSurface();

     DUMP_POOL_STATISTICS(stream << "after evict\n" << poolStatistics());
 }

 void IOSurfacePool::collectInUseSurfaces()
 {
     CachedSurfaceQueue newInUseSurfaces;
     for (CachedSurfaceQueue::iterator surfaceIter = m_inUseSurfaces.begin(); surfaceIter != m_inUseSurfaces.end(); ++surfaceIter) {
         IOSurface* surface = surfaceIter->get();
         if (surface->isInUse()) {
             newInUseSurfaces.append(WTFMove(*surfaceIter));
             continue;
         }

         m_inUseBytesCached -= surface->totalBytes();
         insertSurfaceIntoPool(WTFMove(*surfaceIter));
     }

     m_inUseSurfaces = WTFMove(newInUseSurfaces);
 }

 bool IOSurfacePool::markOlderSurfacesPurgeable()
 {
     bool markedAllSurfaces = true;
     auto markTime = MonotonicTime::now();

     for (auto& surfaceAndDetails : m_surfaceDetails) {
         if (surfaceAndDetails.value.hasMarkedPurgeable)
             continue;

         if (markTime - surfaceAndDetails.value.lastUseTime < surfaceAgeBeforeMarkingPurgeable) {
             markedAllSurfaces = false;
             continue;
         }

         surfaceAndDetails.key->setVolatile(true);
         surfaceAndDetails.value.hasMarkedPurgeable = true;
     }

     return markedAllSurfaces;
 }

 void IOSurfacePool::collectionTimerFired()
 {
     Locker locker { m_lock };
     collectInUseSurfaces();
     bool markedAllSurfaces = markOlderSurfacesPurgeable();

     if (!m_inUseSurfaces.size() && markedAllSurfaces)
         m_collectionTimer.stop();

     platformGarbageCollectNow();
     DUMP_POOL_STATISTICS(stream << "collectionTimerFired\n" << poolStatistics());
 }

 void IOSurfacePool::scheduleCollectionTimer()
 {
     if (!m_collectionTimer.isActive())
         m_collectionTimer.startRepeating(collectionInterval);
 }

 void IOSurfacePool::discardAllSurfaces()
 {
     Locker locker { m_lock };
     discardAllSurfacesInternal();
 }

 void IOSurfacePool::discardAllSurfacesInternal()
 {
     m_bytesCached = 0;
     m_inUseBytesCached = 0;
     m_surfaceDetails.clear();
     m_cachedSurfaces.clear();
     m_inUseSurfaces.clear();
     m_sizesInPruneOrder.clear();
     m_collectionTimer.stop();
     platformGarbageCollectNow();
 }

 String IOSurfacePool::poolStatistics() const
 {
 #if ENABLE_IOSURFACE_POOL_STATISTICS
     TextStream stream;
     stream << "Process " << getpid() << " IOSurfacePool Statistics:\n";

     unsigned totalSurfaces = 0;
     size_t totalSize = 0;
     size_t totalPurgeableSize = 0;

     for (const auto& keyAndSurfaces : m_cachedSurfaces) {
         ASSERT(!keyAndSurfaces.value.isEmpty());
         size_t queueSize = 0;
         size_t queuePurgeableSize = 0;
         for (const auto& surface : keyAndSurfaces.value) {
             size_t surfaceBytes = surface->totalBytes();

             totalSurfaces++;
             queueSize += surfaceBytes;

             if (surface->isVolatile())
                 queuePurgeableSize += surfaceBytes;
         }

         totalSize += queueSize;
         totalPurgeableSize += queuePurgeableSize;

         stream << "   " << keyAndSurfaces.key << ": " << keyAndSurfaces.value.size() << " surfaces for " << queueSize / (1024.0 * 1024.0) << " MB (" << queuePurgeableSize / (1024.0 * 1024.0) << " MB purgeable)\n";
     }

     size_t inUseSize = 0;
     for (const auto& surface : m_inUseSurfaces) {
         totalSurfaces++;
         inUseSize += surface->totalBytes();
     }

     totalSize += inUseSize;
     stream << "   IN USE: " << m_inUseSurfaces.size() << " surfaces for " << inUseSize / (1024.0 * 1024.0) << " MB";

     // FIXME: Should move consistency checks elsewhere, and always perform them in debug builds.
     ASSERT(m_bytesCached == totalSize);
     ASSERT(m_bytesCached <= m_maximumBytesCached);

     stream << "   TOTAL: " << totalSurfaces << " surfaces for " << totalSize / (1024.0 * 1024.0) << " MB (" << totalPurgeableSize / (1024.0 * 1024.0) << " MB purgeable)\n";
     return stream.release();
 #else
     return emptyString();
 #endif
 }

 }
 #endif // HAVE(IOSURFACE)
	/*
	* Copyright (C) 2013, 2014 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. AND ITS 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 APPLE INC. OR ITS 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.
	*/

	#include "config.h"
	#include "IOSurfacePool.h"

	#if HAVE(IOSURFACE)

	#include "DestinationColorSpace.h"
	#include "GraphicsContextCG.h"
	#include <CoreGraphics/CoreGraphics.h>
	#include <wtf/NeverDestroyed.h>
	#include <wtf/text/TextStream.h>

	static const Seconds collectionInterval { 500_ms };
	static const Seconds surfaceAgeBeforeMarkingPurgeable { 2_s };

	#define ENABLE_IOSURFACE_POOL_STATISTICS 0
	#if ENABLE_IOSURFACE_POOL_STATISTICS
	#define DUMP_POOL_STATISTICS(commands) do { ALWAYS_LOG_WITH_STREAM(commands); } while (0);
	#else
	#define DUMP_POOL_STATISTICS(commands) ((void)0)
	#endif

	namespace WebCore {

	IOSurfacePool::IOSurfacePool()
	: m_collectionTimer(RunLoop::main(), this, &IOSurfacePool::collectionTimerFired)
	{
	}

	IOSurfacePool& IOSurfacePool::sharedPool()
	{
	static LazyNeverDestroyed<IOSurfacePool> pool;
	static std::once_flag s_onceFlag;
	std::call_once(s_onceFlag, [] {
	pool.construct();
	});
	return pool;
	}

	Ref<IOSurfacePool> IOSurfacePool::create()
	{
	return adoptRef(*new IOSurfacePool);
	}

	static bool surfaceMatchesParameters(IOSurface& surface, IntSize requestedSize, const DestinationColorSpace& colorSpace, IOSurface::Format format)
	{
	if (format != surface.format())
	return false;
	if (colorSpace != surface.colorSpace())
	return false;
	if (requestedSize != surface.size())
	return false;
	return true;
	}

	void IOSurfacePool::willAddSurface(IOSurface& surface, bool inUse)
	{
	CachedSurfaceDetails& details = m_surfaceDetails.add(&surface, CachedSurfaceDetails()).iterator->value;
	details.resetLastUseTime();

	surface.releaseGraphicsContext();

	size_t surfaceBytes = surface.totalBytes();

	evict(surfaceBytes);

	m_bytesCached += surfaceBytes;
	if (inUse)
	m_inUseBytesCached += surfaceBytes;
	}

	void IOSurfacePool::didRemoveSurface(IOSurface& surface, bool inUse)
	{
	size_t surfaceBytes = surface.totalBytes();
	m_bytesCached -= surfaceBytes;
	if (inUse)
	m_inUseBytesCached -= surfaceBytes;

	m_surfaceDetails.remove(&surface);
	}

	void IOSurfacePool::didUseSurfaceOfSize(IntSize size)
	{
	m_sizesInPruneOrder.remove(m_sizesInPruneOrder.reverseFind(size));
	m_sizesInPruneOrder.append(size);
	}

	std::unique_ptr<IOSurface> IOSurfacePool::takeSurface(IntSize size, const DestinationColorSpace& colorSpace, IOSurface::Format format)
	{
	Locker locker { m_lock };
	CachedSurfaceMap::iterator mapIter = m_cachedSurfaces.find(size);

	if (mapIter == m_cachedSurfaces.end()) {
	DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - failed to find surface matching size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
	return nullptr;
	}

	for (auto surfaceIter = mapIter->value.begin(); surfaceIter != mapIter->value.end(); ++surfaceIter) {
	if (!surfaceMatchesParameters(*surfaceIter->get(), size, colorSpace, format))
	continue;

	auto surface = WTFMove(*surfaceIter);
	mapIter->value.remove(surfaceIter);

	didUseSurfaceOfSize(size);

	if (mapIter->value.isEmpty()) {
	m_cachedSurfaces.remove(mapIter);
	m_sizesInPruneOrder.removeLast();
	}

	didRemoveSurface(*surface, false);

	surface->setVolatile(false);

	DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - taking surface " << surface.get() << " with size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
	return surface;
	}

	// Some of the in-use surfaces may no longer actually be in-use, but we haven't moved them over yet.
	for (auto surfaceIter = m_inUseSurfaces.begin(); surfaceIter != m_inUseSurfaces.end(); ++surfaceIter) {
	if (!surfaceMatchesParameters(*surfaceIter->get(), size, colorSpace, format))
	continue;
	if (surfaceIter->get()->isInUse())
	continue;

	auto surface = WTFMove(*surfaceIter);
	m_inUseSurfaces.remove(surfaceIter);
	didRemoveSurface(*surface, true);

	surface->setVolatile(false);

	DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - taking surface " << surface.get() << " with size " << size << " color space " << colorSpace << " format " << format << "\n" << poolStatistics());
	return surface;
	}

	DUMP_POOL_STATISTICS(stream << "IOSurfacePool::takeSurface - failing\n" << poolStatistics());
	return nullptr;
	}

	bool IOSurfacePool::shouldCacheSurface(const IOSurface& surface) const
	{
	if (surface.totalBytes() > m_maximumBytesCached)
	return false;

	// There's no reason to pool empty surfaces; we should never allocate them in the first place.
	// This also covers isZero(), which would cause trouble when used as the key in m_cachedSurfaces.
	if (surface.size().isEmpty())
	return false;

	return true;
	}

	void IOSurfacePool::addSurface(std::unique_ptr<IOSurface>&& surface)
	{
	Locker locker { m_lock };
	if (!shouldCacheSurface(*surface))
	return;

	bool surfaceIsInUse = surface->isInUse();

	willAddSurface(*surface, surfaceIsInUse);

	if (surfaceIsInUse) {
	m_inUseSurfaces.prepend(WTFMove(surface));
	scheduleCollectionTimer();
	DUMP_POOL_STATISTICS(stream << "addSurface - in-use\n" << poolStatistics());
	return;
	}

	insertSurfaceIntoPool(WTFMove(surface));
	DUMP_POOL_STATISTICS(stream << "addSurface\n" << poolStatistics());
	}

	void IOSurfacePool::insertSurfaceIntoPool(std::unique_ptr<IOSurface> surface)
	{
	IntSize surfaceSize = surface->size();
	auto insertedTuple = m_cachedSurfaces.add(surfaceSize, CachedSurfaceQueue());
	insertedTuple.iterator->value.prepend(WTFMove(surface));
	if (!insertedTuple.isNewEntry)
	m_sizesInPruneOrder.remove(m_sizesInPruneOrder.reverseFind(surfaceSize));
	m_sizesInPruneOrder.append(surfaceSize);

	scheduleCollectionTimer();
	}

	void IOSurfacePool::setPoolSize(size_t poolSizeInBytes)
	{
	Locker locker { m_lock };
	m_maximumBytesCached = poolSizeInBytes;
	evict(0);
	}

	void IOSurfacePool::tryEvictInUseSurface()
	{
	if (m_inUseSurfaces.isEmpty())
	return;

	auto surface = m_inUseSurfaces.takeLast();
	didRemoveSurface(*surface, true);
	}

	void IOSurfacePool::tryEvictOldestCachedSurface()
	{
	if (m_cachedSurfaces.isEmpty())
	return;

	if (m_sizesInPruneOrder.isEmpty())
	return;

	CachedSurfaceMap::iterator surfaceQueueIter = m_cachedSurfaces.find(m_sizesInPruneOrder.first());
	ASSERT(!surfaceQueueIter->value.isEmpty());
	auto surface = surfaceQueueIter->value.takeLast();
	didRemoveSurface(*surface, false);

	if (surfaceQueueIter->value.isEmpty()) {
	m_cachedSurfaces.remove(surfaceQueueIter);
	m_sizesInPruneOrder.remove(0);
	}
	}

	void IOSurfacePool::evict(size_t additionalSize)
	{
	DUMP_POOL_STATISTICS(stream << "before evict\n" << poolStatistics());

	if (additionalSize >= m_maximumBytesCached) {
	discardAllSurfacesInternal();
	DUMP_POOL_STATISTICS(stream << "after evict all\n" << poolStatistics());
	return;
	}

	// FIXME: Perhaps purgeable surfaces should count less against the cap?
	// We don't want to end up with a ton of empty (purged) surfaces, though, as that would defeat the purpose of the pool.
	size_t targetSize = m_maximumBytesCached - additionalSize;

	// Interleave eviction of old cached surfaces and more recent in-use surfaces.
	// In-use surfaces are more recently used, but less useful in the pool, as they aren't
	// immediately available when requested.
	while (m_bytesCached > targetSize) {
	tryEvictOldestCachedSurface();

	if (m_inUseBytesCached > maximumInUseBytes \|\| m_bytesCached > targetSize)
	tryEvictInUseSurface();
	}

	while (m_inUseBytesCached > maximumInUseBytes \|\| m_bytesCached > targetSize)
	tryEvictInUseSurface();

	DUMP_POOL_STATISTICS(stream << "after evict\n" << poolStatistics());
	}

	void IOSurfacePool::collectInUseSurfaces()
	{
	CachedSurfaceQueue newInUseSurfaces;
	for (CachedSurfaceQueue::iterator surfaceIter = m_inUseSurfaces.begin(); surfaceIter != m_inUseSurfaces.end(); ++surfaceIter) {
	IOSurface* surface = surfaceIter->get();
	if (surface->isInUse()) {
	newInUseSurfaces.append(WTFMove(*surfaceIter));
	continue;
	}

	m_inUseBytesCached -= surface->totalBytes();
	insertSurfaceIntoPool(WTFMove(*surfaceIter));
	}

	m_inUseSurfaces = WTFMove(newInUseSurfaces);
	}

	bool IOSurfacePool::markOlderSurfacesPurgeable()
	{
	bool markedAllSurfaces = true;
	auto markTime = MonotonicTime::now();

	for (auto& surfaceAndDetails : m_surfaceDetails) {
	if (surfaceAndDetails.value.hasMarkedPurgeable)
	continue;

	if (markTime - surfaceAndDetails.value.lastUseTime < surfaceAgeBeforeMarkingPurgeable) {
	markedAllSurfaces = false;
	continue;
	}

	surfaceAndDetails.key->setVolatile(true);
	surfaceAndDetails.value.hasMarkedPurgeable = true;
	}

	return markedAllSurfaces;
	}

	void IOSurfacePool::collectionTimerFired()
	{
	Locker locker { m_lock };
	collectInUseSurfaces();
	bool markedAllSurfaces = markOlderSurfacesPurgeable();

	if (!m_inUseSurfaces.size() && markedAllSurfaces)
	m_collectionTimer.stop();

	platformGarbageCollectNow();
	DUMP_POOL_STATISTICS(stream << "collectionTimerFired\n" << poolStatistics());
	}

	void IOSurfacePool::scheduleCollectionTimer()
	{
	if (!m_collectionTimer.isActive())
	m_collectionTimer.startRepeating(collectionInterval);
	}

	void IOSurfacePool::discardAllSurfaces()
	{
	Locker locker { m_lock };
	discardAllSurfacesInternal();
	}

	void IOSurfacePool::discardAllSurfacesInternal()
	{
	m_bytesCached = 0;
	m_inUseBytesCached = 0;
	m_surfaceDetails.clear();
	m_cachedSurfaces.clear();
	m_inUseSurfaces.clear();
	m_sizesInPruneOrder.clear();
	m_collectionTimer.stop();
	platformGarbageCollectNow();
	}

	String IOSurfacePool::poolStatistics() const
	{
	#if ENABLE_IOSURFACE_POOL_STATISTICS
	TextStream stream;
	stream << "Process " << getpid() << " IOSurfacePool Statistics:\n";

	unsigned totalSurfaces = 0;
	size_t totalSize = 0;
	size_t totalPurgeableSize = 0;

	for (const auto& keyAndSurfaces : m_cachedSurfaces) {
	ASSERT(!keyAndSurfaces.value.isEmpty());
	size_t queueSize = 0;
	size_t queuePurgeableSize = 0;
	for (const auto& surface : keyAndSurfaces.value) {
	size_t surfaceBytes = surface->totalBytes();

	totalSurfaces++;
	queueSize += surfaceBytes;

	if (surface->isVolatile())
	queuePurgeableSize += surfaceBytes;
	}

	totalSize += queueSize;
	totalPurgeableSize += queuePurgeableSize;

	stream << " " << keyAndSurfaces.key << ": " << keyAndSurfaces.value.size() << " surfaces for " << queueSize / (1024.0 * 1024.0) << " MB (" << queuePurgeableSize / (1024.0 * 1024.0) << " MB purgeable)\n";
	}

	size_t inUseSize = 0;
	for (const auto& surface : m_inUseSurfaces) {
	totalSurfaces++;
	inUseSize += surface->totalBytes();
	}

	totalSize += inUseSize;
	stream << " IN USE: " << m_inUseSurfaces.size() << " surfaces for " << inUseSize / (1024.0 * 1024.0) << " MB";

	// FIXME: Should move consistency checks elsewhere, and always perform them in debug builds.
	ASSERT(m_bytesCached == totalSize);
	ASSERT(m_bytesCached <= m_maximumBytesCached);

	stream << " TOTAL: " << totalSurfaces << " surfaces for " << totalSize / (1024.0 * 1024.0) << " MB (" << totalPurgeableSize / (1024.0 * 1024.0) << " MB purgeable)\n";
	return stream.release();
	#else
	return emptyString();
	#endif
	}

	}
	#endif // HAVE(IOSURFACE)