This adds periodic OOM score adjustment, based on the last access time

chrome/browser/oom_priority_manager.h

+// Copyright (c) 2010 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 CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_
+#define CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_
+
+#include "base/timer.h"
+
+namespace browser {
+
+// The OomPriorityManager periodically checks (see
+// ADJUSTMENT_INTERVAL_SECONDS in the source) the status of renderers
+// and adjusts the out of memory (OOM) adjustment value (in
+// /proc/<pid>/oom_adj) of the renderers so that they match the
+// algorithm embedded here for priority in being killed upon OOM
+// conditions.
+//
+// The algorithm used favors killing tabs that are not pinned, have
+// been idle for longest, and take up the most memory, in that order
+// of priority.  We round the idle times to the nearest few minutes
+// (see BUCKET_INTERVAL_MINUTES in the source) so that we can bucket
+// them, as no two tabs will have exactly the same idle time.
+class OomPriorityManager {
+ public:
+  OomPriorityManager();
+  ~OomPriorityManager();
+
+ private:
+  void StartTimer();
+  void StopTimer();
+
+  // Starts DoAdjustOomPriorities on the file threadead.  Called when the
+  // timer fires.
+  void AdjustOomPriorities();
+
+  // Called by AdjustOomPriorities.  Runs on the file thread.
+  void DoAdjustOomPriorities();
+
+  base::RepeatingTimer<OomPriorityManager> timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
+};
+}  // namespace browser
+
+DISABLE_RUNNABLE_METHOD_REFCOUNT(browser::OomPriorityManager);
+
+#endif  // CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_