зеркало из https://github.com/mozilla/gecko-dev.git
89 строки
2.8 KiB
C++
89 строки
2.8 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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#ifndef mozilla_gfx_layers_mlgpu_BufferCache_h
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#define mozilla_gfx_layers_mlgpu_BufferCache_h
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#include "mozilla/EnumeratedArray.h"
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#include "mozilla/RefPtr.h"
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#include <deque>
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#include <vector>
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namespace mozilla {
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namespace layers {
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class MLGBuffer;
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class MLGDevice;
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// Cache MLGBuffers based on how long ago they were last used.
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class BufferCache
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{
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public:
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explicit BufferCache(MLGDevice* aDevice);
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~BufferCache();
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// Get a buffer that has at least |aBytes|, or create a new one
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// if none can be re-used.
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RefPtr<MLGBuffer> GetOrCreateBuffer(size_t aBytes);
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// Age out old buffers after a frame has been completed.
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void EndFrame();
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private:
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// Not RefPtr since this would create a cycle.
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MLGDevice* mDevice;
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// The first size class is Log2(N), where 16 is the minimum size of a
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// constant buffer (currently 16 bytes).
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size_t mFirstSizeClass;
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// Each size class is a power of 2. Each pool of buffers is represented as a
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// deque, with the least-recently-used (i.e., oldest) buffers at the front,
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// and most-recently-used (i.e., newest) buffers at the back. To re-use a
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// buffer it is popped off the front and re-added to the back.
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//
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// This is not always efficient use of storage: if a single frame allocates
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// 300 buffers of the same size, we may keep recycling through all those
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// buffers for a long time, as long as at least one gets used per frame.
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// But since buffers use tiny amounts of memory, and they are only mapped
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// while drawing, it shouldn't be a big deal.
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struct CacheEntry {
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CacheEntry() : mLastUsedFrame(0)
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{}
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CacheEntry(const CacheEntry& aEntry)
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: mLastUsedFrame(aEntry.mLastUsedFrame),
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mBuffer(aEntry.mBuffer)
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{}
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CacheEntry(CacheEntry&& aEntry)
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: mLastUsedFrame(aEntry.mLastUsedFrame),
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mBuffer(Move(aEntry.mBuffer))
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{}
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CacheEntry(size_t aLastUsedFrame, MLGBuffer* aBuffer)
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: mLastUsedFrame(aLastUsedFrame),
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mBuffer(aBuffer)
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{}
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uint64_t mLastUsedFrame;
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RefPtr<MLGBuffer> mBuffer;
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};
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typedef std::deque<CacheEntry> CachePool;
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// We track how many frames have occurred to determine the age of cache entries.
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uint64_t mFrameNumber;
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// To avoid doing too much work in one frame, we only shrink one size class
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// per frame.
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uint64_t mNextSizeClassToShrink;
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// There is one pool of buffers for each power of 2 allocation size. The
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// maximum buffer size is at most 64KB on Direct3D 11.
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std::vector<CachePool> mCaches;
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};
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} // namespace layers
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} // namespace mozilla
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#endif // mozilla_gfx_layers_mlgpu_BufferCache_h
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