forked from mirrors/gecko-dev
127 lines
3.5 KiB
C++
127 lines
3.5 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "BufferCache.h"
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#include "MLGDevice.h"
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#include "mozilla/MathAlgorithms.h"
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namespace mozilla {
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namespace layers {
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BufferCache::BufferCache(MLGDevice* aDevice)
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: mDevice(aDevice)
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{
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}
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BufferCache::~BufferCache()
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{
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}
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RefPtr<MLGBuffer>
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BufferCache::GetOrCreateBuffer(size_t aBytes)
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{
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// Try to take a buffer from the expired frame. If none exists, make a new one.
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RefPtr<MLGBuffer> buffer = mExpired.Take(aBytes);
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if (!buffer) {
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// Round up to the nearest size class, but not over 1024 bytes.
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size_t roundedUp = std::max(std::min(RoundUpPow2(aBytes), size_t(1024)), aBytes);
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buffer = mDevice->CreateBuffer(MLGBufferType::Constant, roundedUp, MLGUsage::Dynamic, nullptr);
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if (!buffer) {
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return nullptr;
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}
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}
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MOZ_ASSERT(buffer->GetSize() >= aBytes);
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// Assign this buffer to the current frame, so it becomes available again once
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// this frame expires.
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mCurrent.Put(buffer);
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return buffer;
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}
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void
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BufferCache::EndFrame()
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{
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BufferPool empty;
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mExpired = Move(mPrevious);
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mPrevious = Move(mCurrent);
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mCurrent = Move(empty);
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}
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RefPtr<MLGBuffer>
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BufferPool::Take(size_t aBytes)
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{
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MOZ_ASSERT(aBytes >= 16);
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// We need to bump the request up to the nearest size class. For example,
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// a request of 24 bytes must allocate from the 32 byte pool.
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SizeClass sc = GetSizeClassFromHighBit(CeilingLog2(aBytes));
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if (sc == SizeClass::Huge) {
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return TakeHugeBuffer(aBytes);
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}
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if (mClasses[sc].IsEmpty()) {
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return nullptr;
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}
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RefPtr<MLGBuffer> buffer = mClasses[sc].LastElement();
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mClasses[sc].RemoveElementAt(mClasses[sc].Length() - 1);
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return buffer.forget();
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}
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void
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BufferPool::Put(MLGBuffer* aBuffer)
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{
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MOZ_ASSERT(aBuffer->GetSize() >= 16);
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// When returning buffers, we bump them into a lower size class. For example
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// a 24 byte buffer cannot be re-used for a 32-byte allocation, so it goes
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// into the 16-byte class.
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SizeClass sc = GetSizeClassFromHighBit(FloorLog2(aBuffer->GetSize()));
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if (sc == SizeClass::Huge) {
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mHugeBuffers.push_back(aBuffer);
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} else {
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mClasses[sc].AppendElement(aBuffer);
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}
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}
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RefPtr<MLGBuffer>
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BufferPool::TakeHugeBuffer(size_t aBytes)
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{
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static const size_t kMaxSearches = 3;
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size_t numSearches = std::min(kMaxSearches, mHugeBuffers.size());
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for (size_t i = 0; i < numSearches; i++) {
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RefPtr<MLGBuffer> buffer = mHugeBuffers.front();
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mHugeBuffers.pop_front();
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// Don't pick buffers that are massively overallocated.
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if (buffer->GetSize() >= aBytes && buffer->GetSize() <= aBytes * 2) {
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return buffer.forget();
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}
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// Return the buffer to the list.
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mHugeBuffers.push_back(buffer);
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}
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return nullptr;
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}
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/* static */ BufferPool::SizeClass
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BufferPool::GetSizeClassFromHighBit(size_t aBit)
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{
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// If the size is smaller than our smallest size class (which should
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// never happen), or bigger than our largest size class, we dump it
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// in the catch-all "huge" list.
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static const size_t kBitForFirstClass = 4;
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static const size_t kBitForLastClass = kBitForFirstClass + size_t(SizeClass::Huge);
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if (aBit < kBitForFirstClass || aBit >= kBitForLastClass) {
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return SizeClass::Huge;
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}
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return SizeClass(aBit - kBitForFirstClass);
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}
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} // namespace layers
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} // namespace mozilla
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