Do V8 GC ASAP if system memory is pressured

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 12e31bd84c93b5922bd24fa8094c46a8ead06434..d3e36869968d4fa513a6e753f398ed0992d59345 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -163,7 +163,6 @@
 #include "third_party/skia/include/core/SkGraphics.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_base_switches.h"
-#include "v8/include/v8.h"
 
 #if defined(OS_ANDROID)
 #include <cpu-features.h>
@@ -818,7 +817,9 @@ void RenderThreadImpl::Init() {
 #endif
 
   memory_pressure_listener_.reset(new base::MemoryPressureListener(
-      base::Bind(&RenderThreadImpl::OnMemoryPressure, base::Unretained(this))));
+      base::Bind(&RenderThreadImpl::OnMemoryPressure, base::Unretained(this)),
+      base::Bind(&RenderThreadImpl::IsMemoryPressured,
+                 base::Unretained(this))));
 
   int num_raster_threads = 0;
   std::string string_value =
@@ -2014,6 +2015,7 @@ void RenderThreadImpl::OnCreateNewSharedWorker(
 
 void RenderThreadImpl::OnMemoryPressure(
     base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
+  TRACE_EVENT0("memory","RenderThreadImpl::OnMemoryPressure");
   ReleaseFreeMemory();
 
   // Do not call into blink if it is not initialized.
@@ -2026,7 +2028,11 @@ void RenderThreadImpl::OnMemoryPressure(
       // This will potentially hang the renderer for a long time, however, when
       // we receive a memory pressure notification, we might be about to be
       // killed.
-      blink::mainThreadIsolate()->LowMemoryNotification();
+      if (is_v8_need_gc_) {
+        blink::mainThreadIsolate()->LowMemoryNotification();
+        is_v8_need_gc_ = false;
+      }
+
       RenderThread::Get()->PostTaskToAllWebWorkers(
           base::Bind(&LowMemoryNotificationOnThisThread));
     }
@@ -2185,4 +2191,18 @@ void RenderThreadImpl::PendingRenderFrameConnect::OnConnectionError() {
   DCHECK_EQ(1u, erased);
 }
 
+void RenderThreadImpl::OnV8InterruptCallback(v8::Isolate* isolate, void* data) {
+  RenderThreadImpl* pRenderThreadImpl =
+      reinterpret_cast<RenderThreadImpl*>(data);
+  if (!pRenderThreadImpl || !pRenderThreadImpl->is_v8_need_gc_)
+    return;
+  blink::mainThreadIsolate()->LowMemoryNotification();

[esprehn, 2016/03/01 22:15:07]

Is this safe? You're using the LowMemoryNotification method on Isolate from the
wrong thread, I don't think that's okay.

+  pRenderThreadImpl->is_v8_need_gc_ = false;
+}
+
+void RenderThreadImpl::IsMemoryPressured(bool memory_pressured) {
+  is_v8_need_gc_ = true;
+  blink::mainThreadIsolate()->RequestInterrupt(&OnV8InterruptCallback, this);

[jochen (gone - plz use gerrit), 2016/03/02 07:59:38]

the interrupt callback must not reenter V8.

+}
+
 }  // namespace content