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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SharedContextRateLimiter_h
#define SharedContextRateLimiter_h
#include "gpu/command_buffer/client/gles2_interface.h"
#include "wtf/Allocator.h"
#include "wtf/Deque.h"
#include "wtf/Noncopyable.h"
#include <memory>
namespace blink {
class WebGraphicsContext3DProvider;
// Purpose: to limit the amount of worked queued for execution
// (backlog) on the GPU by blocking the main thread to allow the GPU
// to catch up. The Prevents unsynchronized tight animation loops
// from cause a GPU denial of service.
//
// How it works: The rate limiter uses GPU fences to mark each tick
// and makes sure there are never more that 'maxPendingTicks' fences
// that are awaiting completion. On platforms that do not support
// fences, we use glFinish instead. glFinish will only be called in
// unsynchronized cases that submit more than maxPendingTicks animation
// tick per compositor frame, which should be quite rare.
//
// How to use it: Each unit of work that constitutes a complete animation
// frame must call tick(). reset() must be called when the animation
// is consumed by committing to the compositor. Several rate limiters can
// be used concurrently: they will each use their own sequences of
// fences which may be interleaved. When the graphics context is lost
// and later restored, the existing rate limiter must be destroyed and
// a new one created.
class SharedContextRateLimiter final {
USING_FAST_MALLOC(SharedContextRateLimiter);
WTF_MAKE_NONCOPYABLE(SharedContextRateLimiter);
public:
static std::unique_ptr<SharedContextRateLimiter> create(
unsigned maxPendingTicks);
void tick();
void reset();
private:
SharedContextRateLimiter(unsigned maxPendingTicks);
std::unique_ptr<WebGraphicsContext3DProvider> m_contextProvider;
Deque<GLuint> m_queries;
unsigned m_maxPendingTicks;
bool m_canUseSyncQueries;
};
} // namespace blink
#endif
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