memory coordinator: Purge memory under memory pressure

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <utility>
@@ skipping 2217 matching lines @@
 }
 
 void RenderThreadImpl::OnMemoryStateChange(base::MemoryState state) {
   if (blink_platform_impl_) {
     blink::WebMemoryCoordinator::onMemoryStateChange(
         static_cast<blink::MemoryState>(state));
   }
 }
 
 void RenderThreadImpl::OnPurgeMemory() {
+  // Record amount of purged memory after 2 seconds. 2 seconds is arbitrary
+  // but it works most cases.
+  RendererMemoryMetrics metrics;
+  GetRendererMemoryMetrics(&metrics);
+  GetRendererScheduler()->DefaultTaskRunner()->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&RenderThreadImpl::RecordPurgeMemory, base::Unretained(this),
+                 std::move(metrics)),
+      base::TimeDelta::FromSeconds(2));
+
   OnTrimMemoryImmediately();
   ReleaseFreeMemory();
   ClearMemory();
   if (blink_platform_impl_)
     blink::WebMemoryCoordinator::onPurgeMemory();
 }
 
+void RenderThreadImpl::RecordPurgeMemory(RendererMemoryMetrics before) {
+  RendererMemoryMetrics after;
+  GetRendererMemoryMetrics(&after);
+  int64_t mbytes = static_cast<int64_t>(before.total_allocated_mb) -
+                   static_cast<int64_t>(after.total_allocated_mb);
+  if (mbytes < 0)
+    mbytes = 0;
+  UMA_HISTOGRAM_MEMORY_LARGE_MB("Memory.Experimental.Renderer.PurgedMemory",
+                                mbytes);
+}
+
 void RenderThreadImpl::ClearMemory() {
   // Do not call into blink if it is not initialized.
   if (blink_platform_impl_) {
     // Purge Skia font cache, by setting it to 0 and then again to the
     // previous limit.
     size_t font_cache_limit = SkGraphics::SetFontCacheLimit(0);
     SkGraphics::SetFontCacheLimit(font_cache_limit);
   }
 }
 
@@ skipping 177 matching lines @@
   }
 }
 
 void RenderThreadImpl::OnRendererInterfaceRequest(
     mojom::RendererAssociatedRequest request) {
   DCHECK(!renderer_binding_.is_bound());
   renderer_binding_.Bind(std::move(request));
 }
 
 }  // namespace content