Add a ticks counter that tells you how idle is a render process

It gives you a timedelta since the last time it was known that the renderer was active

- so far receiving a message from the renderer seems a simple heuristic.
- The goal is to use it to prioritize the use of hot renderers or do something to cold ones.

BUG=none
TEST=test included


Review URL: http://codereview.chromium.org/267018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@28469 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 36 insertions, 0 deletions

diff --git a/chrome/browser/browser_browsertest.cc b/chrome/browser/browser_browsertest.cc
index 930c0b3..922f382 100644
--- a/chrome/browser/browser_browsertest.cc
+++ b/chrome/browser/browser_browsertest.cc
@@ -181,3 +181,17 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, SingleBeforeUnloadAfterWindowClose) {
   alert->AcceptWindow();
 }
 
+// Test that get_process_idle_time() returns reasonable values when compared
+// with time deltas measured locally.
+IN_PROC_BROWSER_TEST_F(BrowserTest, RenderIdleTime) {
+  base::TimeTicks start = base::TimeTicks::Now();
+  ui_test_utils::NavigateToURL(browser(),
+                               ui_test_utils::GetTestUrl(L".", L"title1.html"));
+  RenderProcessHost::iterator it(RenderProcessHost::AllHostsIterator());
+  for (; !it.IsAtEnd(); it.Advance()) {
+    base::TimeDelta renderer_td =
+        it.GetCurrentValue()->get_child_process_idle_time();
+    base::TimeDelta browser_td = base::TimeTicks::Now() - start;
+    EXPECT_TRUE(browser_td >= renderer_td);
+  }
+}
diff --git a/chrome/browser/renderer_host/browser_render_process_host.cc b/chrome/browser/renderer_host/browser_render_process_host.cc
index d699592..35df945 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.cc
+++ b/chrome/browser/renderer_host/browser_render_process_host.cc
@@ -781,6 +781,7 @@ bool BrowserRenderProcessHost::Send(IPC::Message* msg) {
 }
 
 void BrowserRenderProcessHost::OnMessageReceived(const IPC::Message& msg) {
+  mark_child_process_activity_time();
   if (msg.routing_id() == MSG_ROUTING_CONTROL) {
     // dispatch control messages
     bool msg_is_ok = true;
@@ -860,6 +861,7 @@ void BrowserRenderProcessHost::OnChannelConnected(int32 peer_pid) {
       CHECK(peer_pid == process_.pid()) << peer_pid << " " << process_.pid();
 #endif
     }
+    mark_child_process_activity_time();
   }
 
 #if defined(IPC_MESSAGE_LOG_ENABLED)
diff --git a/chrome/browser/renderer_host/render_process_host.cc b/chrome/browser/renderer_host/render_process_host.cc
index 6cefab0..5f9363e 100644
--- a/chrome/browser/renderer_host/render_process_host.cc
+++ b/chrome/browser/renderer_host/render_process_host.cc
@@ -85,6 +85,8 @@ RenderProcessHost::RenderProcessHost(Profile* profile)
       ignore_input_events_(false) {
   all_hosts.AddWithID(this, id());
   all_hosts.set_check_on_null_data(true);
+  // Initialize |child_process_activity_time_| to a reasonable value.
+  mark_child_process_activity_time();
 }
 
 RenderProcessHost::~RenderProcessHost() {
diff --git a/chrome/browser/renderer_host/render_process_host.h b/chrome/browser/renderer_host/render_process_host.h
index f266e53..4014b63 100644
--- a/chrome/browser/renderer_host/render_process_host.h
+++ b/chrome/browser/renderer_host/render_process_host.h
@@ -11,6 +11,7 @@
 #include "base/id_map.h"
 #include "base/process.h"
 #include "base/scoped_ptr.h"
+#include "base/time.h"
 #include "chrome/common/transport_dib.h"
 #include "chrome/common/visitedlink_common.h"
 #include "ipc/ipc_sync_channel.h"
@@ -108,6 +109,20 @@ class RenderProcessHost : public IPC::Channel::Sender,
     return ignore_input_events_;
   }
 
+  // Returns how long the child has been idle. The definition of idle
+  // depends on when a derived class calls mark_child_process_activity_time().
+  // This is a rough indicator and its resolution should not be better than
+  // 10 milliseconds.
+  base::TimeDelta get_child_process_idle_time() const {
+    return base::TimeTicks::Now() - child_process_activity_time_;
+  }
+
+  // Call this function when it is evident that the child process is actively
+  // performing some operation, for example if we just received an IPC message.
+  void mark_child_process_activity_time() {
+    child_process_activity_time_ = base::TimeTicks::Now();
+  }
+
   // Try to shutdown the associated render process as fast as possible, but
   // only if |count| matches the number of render widgets that this process
   // controls.
@@ -263,6 +278,9 @@ class RenderProcessHost : public IPC::Channel::Sender,
   // See getter above.
   static bool run_renderer_in_process_;
 
+  // Records the last time we regarded the child process active.
+  base::TimeTicks child_process_activity_time_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHost);
 };