Do not kill recently killed ARC processes again

chrome/browser/memory/tab_manager_delegate_chromeos.h

 // Copyright 2015 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_MEMORY_TAB_MANAGER_DELEGATE_CHROMEOS_H_
 #define CHROME_BROWSER_MEMORY_TAB_MANAGER_DELEGATE_CHROMEOS_H_
 
 #include <memory>
+#include <string>
 #include <utility>
 #include <vector>
 
 #include "base/containers/hash_tables.h"
 #include "base/gtest_prod_util.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/process/process.h"
 #include "base/timer/timer.h"
@@ skipping 52 matching lines @@
   void LowMemoryKill(const TabStatsList& tab_stats);
 
   // Returns oom_score_adj of a process if the score is cached by |this|.
   // If couldn't find the score in the cache, returns -1001 since the valid
   // range of oom_score_adj is [-1000, 1000].
   int GetCachedOomScore(base::ProcessHandle process_handle);
 
   // Called when the timer fires, sets oom_adjust_score for all renderers.
   void AdjustOomPriorities(const TabStatsList& tab_list);
 
+  // Returns true if the process has recently been killed.
+  // Virtual for unit testing.
+  virtual bool IsRecentlyKilledArcProcess(const std::string& process_name,
+                                          const base::TimeTicks& now);
+
  protected:
   // Kills an ARC process. Returns true if the kill request is successfully sent
   // to Android. Virtual for unit testing.
   virtual bool KillArcProcess(const int nspid);
 
   // Kills a tab. Returns true if the tab is killed successfully.
   // Virtual for unit testing.
   virtual bool KillTab(int64_t tab_id);
 
-  // Get debugd client instance.
+  // Get debugd client instance. Virtual for unit testing.
   virtual chromeos::DebugDaemonClient* GetDebugDaemonClient();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(TabManagerDelegateTest, CandidatesSorted);
+  FRIEND_TEST_ALL_PREFIXES(TabManagerDelegateTest, IsRecentlyKilledArcProcess);
+  FRIEND_TEST_ALL_PREFIXES(TabManagerDelegateTest,
+                           DoNotKillRecentlyKilledArcProcesses);
   FRIEND_TEST_ALL_PREFIXES(TabManagerDelegateTest, KillMultipleProcesses);
   FRIEND_TEST_ALL_PREFIXES(TabManagerDelegateTest, SetOomScoreAdj);
 
   class Candidate;
   class FocusedProcess;
 
   friend std::ostream& operator<<(std::ostream& out,
                                   const Candidate& candidate);
 
   // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // Pair to hold child process host id and ProcessHandle.
   typedef std::pair<int, base::ProcessHandle> ProcessInfo;
 
   // Cache OOM scores in memory.
   typedef base::hash_map<base::ProcessHandle, int> ProcessScoreMap;
 
+  // A map from an ARC process name to a monotonic timestamp when it's killed.
+  typedef base::hash_map<std::string, base::TimeTicks> KilledArcProcessesMap;
+
   // Get the list of candidates to kill, sorted by descending importance.
   static std::vector<Candidate> GetSortedCandidates(
       const TabStatsList& tab_list,
       const std::vector<arc::ArcProcess>& arc_processes);
 
   // Sets OOM score for the focused tab.
   void OnFocusTabScoreAdjustmentTimeout();
 
   // Kills a process after getting all info of tabs and apps.
   void LowMemoryKillImpl(const TabStatsList& tab_list,
@@ skipping 17 matching lines @@
   void DistributeOomScoreInRange(
       std::vector<TabManagerDelegate::Candidate>::const_iterator begin,
       std::vector<TabManagerDelegate::Candidate>::const_iterator end,
       int range_begin,
       int range_end,
       ProcessScoreMap* new_map);
 
   // Initiates an oom priority adjustment.
   void ScheduleEarlyOomPrioritiesAdjustment();
 
+  // A constant to avoid killing a process too often. ARC processes sometimes
+  // respawn right after being killed. In that case, killing them every time
+  // is just a waste of resources.
+  static const int64_t kArcSkipKillingTimeInSeconds;

[Luis Héctor Chávez, 2017/05/02 20:16:27]

nit: maybe call this kArcRespawnKillDelay or kArcRecentlyKilledDelay.

Also, can this be a base::TimeDelta? It is just a very thin wrapper around an
int64_t, so type-wise it should be fine.

[Yusuke Sato, 2017/05/02 20:47:32]

Done. Following the offline discussion, added a static function that returns a
constexpr TimeDelta object.

+
   // Holds a reference to the owning TabManager.
   const base::WeakPtr<TabManager> tab_manager_;
 
   // Registrar to receive renderer notifications.
   content::NotificationRegistrar registrar_;
 
   // Timer to guarantee that the tab or app is focused for a certain amount of
   // time.
   base::OneShotTimer focus_process_score_adjust_timer_;
   // Holds the info of the newly focused tab or app. Its OOM score would be
   // adjusted when |focus_process_score_adjust_timer_| is expired.
   std::unique_ptr<FocusedProcess> focused_process_;
 
   // Map maintaining the process handle - oom_score mapping.
   ProcessScoreMap oom_score_map_;
 
+  // Map maintaing ARC process names and their last killed time.
+  KilledArcProcessesMap recently_killed_arc_processes_;
+
   // Util for getting system memory status.
   std::unique_ptr<TabManagerDelegate::MemoryStat> mem_stat_;
 
   // Weak pointer factory used for posting tasks to other threads.
   base::WeakPtrFactory<TabManagerDelegate> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TabManagerDelegate);
 };
 
 // On ARC enabled machines, either a tab or an app could be a possible
@@ skipping 51 matching lines @@
   // reported if available memory is under the number.
   static int LowMemoryMarginKB();
 
   // Reads in an integer.
   static int ReadIntFromFile(const char* file_name, int default_val);
 };
 
 }  // namespace memory
 
 #endif  // CHROME_BROWSER_MEMORY_TAB_MANAGER_DELEGATE_CHROMEOS_H_