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// 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.
#ifndef CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_
#define CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_
#include <vector>
#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/hash_tables.h"
#include "base/memory/scoped_ptr.h"
#include "base/process.h"
#include "base/string16.h"
#include "base/synchronization/lock.h"
#include "base/time.h"
#include "base/timer.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"
namespace browser {
class LowMemoryObserver;
// 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_score_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 selected, not pinned,
// and have been idle for longest, in that order of priority.
class OomPriorityManager : public content::NotificationObserver {
public:
OomPriorityManager();
virtual ~OomPriorityManager();
void Start();
void Stop();
// Returns list of tab titles sorted from most interesting (don't kill)
// to least interesting (OK to kill).
std::vector<string16> GetTabTitles();
// Discards a tab to free the memory occupied by its renderer.
// Tab still exists in the tab-strip; clicking on it will reload it.
// Returns true if it successfully found a tab and discarded it.
bool DiscardTab();
private:
FRIEND_TEST_ALL_PREFIXES(OomPriorityManagerTest, Comparator);
struct TabStats {
TabStats();
~TabStats();
bool is_pinned;
bool is_selected;
base::TimeTicks last_selected;
base::ProcessHandle renderer_handle;
bool sudden_termination_allowed;
string16 title;
int64 tab_contents_id; // unique ID per WebContents
};
typedef std::vector<TabStats> TabStatsList;
// Discards a tab with the given unique ID. Returns true if discard occurred.
bool DiscardTabById(int64 target_web_contents_id);
// Records UMA histogram statistics for a tab discard. We record statistics
// for user triggered discards via chrome://discards/ because that allows us
// to manually test the system.
void RecordDiscardStatistics();
// Returns the number of tabs open in all browser instances.
int GetTabCount() const;
TabStatsList GetTabStatsOnUIThread();
// Called when the timer fires, sets oom_adjust_score for all renderers.
void AdjustOomPriorities();
// Called by AdjustOomPriorities.
void AdjustOomPrioritiesOnFileThread(TabStatsList stats_list);
// Posts AdjustFocusedTabScore task to the file thread.
void OnFocusTabScoreAdjustmentTimeout();
// Sets the score of the focused tab to the least value.
void AdjustFocusedTabScoreOnFileThread();
static bool CompareTabStats(TabStats first, TabStats second);
virtual void Observe(int type,
const content::NotificationSource& source,
const content::NotificationDetails& details) OVERRIDE;
base::RepeatingTimer<OomPriorityManager> timer_;
base::OneShotTimer<OomPriorityManager> focus_tab_score_adjust_timer_;
content::NotificationRegistrar registrar_;
// This lock is for pid_to_oom_score_ and focus_tab_pid_.
base::Lock pid_to_oom_score_lock_;
// map maintaining the process - oom_score mapping.
typedef base::hash_map<base::ProcessHandle, int> ProcessScoreMap;
ProcessScoreMap pid_to_oom_score_;
base::ProcessHandle focused_tab_pid_;
scoped_ptr<LowMemoryObserver> low_memory_observer_;
// Wall-clock time when the priority manager started running.
base::TimeTicks start_time_;
// Wall-clock time of last tab discard during this browsing session, or 0 if
// no discard has happened yet.
base::TimeTicks last_discard_time_;
// Wall-clock time of last priority adjustment, used to correct the above
// times for discontinuities caused by suspend/resume.
base::TimeTicks last_adjust_time_;
// Number of times we have discarded a tab, for statistics.
int discard_count_;
DISALLOW_COPY_AND_ASSIGN(OomPriorityManager);
};
} // namespace browser
#endif // CHROME_BROWSER_OOM_PRIORITY_MANAGER_H_
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