Idle cleanup for worker context

cc/output/context_cache_controller.cc

 // Copyright (c) 2016 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.
 
 #include "cc/output/context_cache_controller.h"
 
+#include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
 #include "gpu/command_buffer/client/context_support.h"
 #include "third_party/skia/include/gpu/GrContext.h"
 
 namespace cc {
-ContextCacheController::ScopedVisibility::ScopedVisibility() = default;
+namespace {
+static const int kIdleCleanupDelaySeconds = 1;
+}  // namespace
 
-ContextCacheController::ScopedVisibility::~ScopedVisibility() {
+ContextCacheController::ScopedToken::ScopedToken() = default;
+
+ContextCacheController::ScopedToken::~ScopedToken() {
   DCHECK(released_);
 }
 
-void ContextCacheController::ScopedVisibility::Release() {
+void ContextCacheController::ScopedToken::Release() {
   DCHECK(!released_);
   released_ = true;
 }
 
 ContextCacheController::ContextCacheController(
     gpu::ContextSupport* context_support,
     scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-    : context_support_(context_support), task_runner_(std::move(task_runner)) {}
+    : context_support_(context_support),
+      task_runner_(std::move(task_runner)),
+      weak_factory_(this) {
+  // The |weak_factory_| can only be used from a single thread. We
+  // create/destroy this class and run callbacks on a single thread, but we
+  // want to be able to post callbacks from multiple threads. We need a weak
+  // ptr to post callbacks, so acquire one here, while we're on the right
+  // thread.
+  weak_ptr_ = weak_factory_.GetWeakPtr();
+}
 
 ContextCacheController::~ContextCacheController() = default;
 
 void ContextCacheController::SetGrContext(GrContext* gr_context) {
   gr_context_ = gr_context;
 }
 
+void ContextCacheController::SetLock(base::Lock* lock) {
+  context_lock_ = lock;
+}
+
 std::unique_ptr<ContextCacheController::ScopedVisibility>
 ContextCacheController::ClientBecameVisible() {
+  if (context_lock_)
+    context_lock_->AssertAcquired();
+
   bool became_visible = num_clients_visible_ == 0;
   ++num_clients_visible_;
 
   if (became_visible)
     context_support_->SetAggressivelyFreeResources(false);
 
   return base::WrapUnique(new ScopedVisibility());
 }
 
 void ContextCacheController::ClientBecameNotVisible(
     std::unique_ptr<ScopedVisibility> scoped_visibility) {
   DCHECK(scoped_visibility);
   scoped_visibility->Release();
 
+  if (context_lock_)
+    context_lock_->AssertAcquired();
+
   DCHECK_GT(num_clients_visible_, 0u);
   --num_clients_visible_;
 
   if (num_clients_visible_ == 0) {
+    // We are freeing resources now - cancel any pending idle callbacks.
+    InvalidatePendingIdleCallbacks();
+
     if (gr_context_)
       gr_context_->freeGpuResources();
     context_support_->SetAggressivelyFreeResources(true);
   }
 }
 
-std::unique_ptr<ContextCacheController::ScopedVisibility>
-ContextCacheController::CreateScopedVisibilityForTesting() const {
-  return base::WrapUnique(new ScopedVisibility());
+std::unique_ptr<ContextCacheController::ScopedBusy>
+ContextCacheController::ClientBecameBusy() {
+  if (context_lock_)
+    context_lock_->AssertAcquired();
+
+  ++num_clients_busy_;
+  // We are busy, cancel any pending idle callbacks.
+  InvalidatePendingIdleCallbacks();
+
+  return base::WrapUnique(new ScopedBusy());
 }
 
-void ContextCacheController::ReleaseScopedVisibilityForTesting(
-    std::unique_ptr<ScopedVisibility> scoped_visibility) const {
-  scoped_visibility->Release();
+void ContextCacheController::ClientBecameNotBusy(
+    std::unique_ptr<ScopedBusy> scoped_busy) {
+  DCHECK(scoped_busy);
+  scoped_busy->Release();
+
+  if (context_lock_)
+    context_lock_->AssertAcquired();
+
+  DCHECK_GT(num_clients_busy_, 0u);
+  --num_clients_busy_;
+
+  // If we have become idle and we are visible, queue a task to drop resources
+  // after a delay. If are not visible, we have already dropped resources.
+  if (num_clients_busy_ == 0 && num_clients_visible_ > 0 && task_runner_) {
+    // If we already have a callback pending, don't post a new one. The pending
+    // callback will handle posting a new callback itself. This prevents us from
+    // flooding the system with tasks.
+    if (!callback_pending_) {
+      {
+        base::AutoLock hold(current_idle_generation_lock_);
+        PostIdleCallback(current_idle_generation_);
+      }
+      callback_pending_ = true;
+    }
+  }
+}
+
+void ContextCacheController::PostIdleCallback(
+    uint32_t current_idle_generation) const {
+  task_runner_->PostDelayedTask(
+      FROM_HERE, base::Bind(&ContextCacheController::OnIdle, weak_ptr_,
+                            current_idle_generation),
+      base::TimeDelta::FromSeconds(kIdleCleanupDelaySeconds));
+}
+
+void ContextCacheController::InvalidatePendingIdleCallbacks() {
+  base::AutoLock hold(current_idle_generation_lock_);
+  ++current_idle_generation_;
+}
+
+void ContextCacheController::OnIdle(uint32_t idle_generation) {
+  // First check if we should run our idle callback at all. If we have become
+  // busy since scheduling, just schedule another idle callback and return.
+  {
+    base::AutoLock hold(current_idle_generation_lock_);
+    if (current_idle_generation_ != idle_generation) {
+      PostIdleCallback(current_idle_generation_);
+      return;
+    }
+  }
+
+  // Try to acquire the context lock - if we can't acquire it then we've become
+  // busy since checking |current_idle_generation_| above. In this case, just
+  // re-post our idle callback and return.
+  if (context_lock_ && !context_lock_->Try()) {
+    base::AutoLock hold(current_idle_generation_lock_);
+    PostIdleCallback(current_idle_generation_);
+    return;
+  }
+
+  if (gr_context_)
+    gr_context_->freeGpuResources();
+
+  // Toggle SetAggressivelyFreeResources to drop command buffer data.
+  context_support_->SetAggressivelyFreeResources(true);
+  context_support_->SetAggressivelyFreeResources(false);
+
+  callback_pending_ = false;
+
+  if (context_lock_)
+    context_lock_->Release();
 }
 
 }  // namespace cc