Bug 1212833 - Delay the MemoryPressure when an application goes to background. r=gsvelto

b2g/app/b2g.js

@@ -693,6 +693,7 @@ pref("layout.css.scroll-snap.enabled", true);
 pref("dom.ipc.processPriorityManager.enabled", true);
 pref("dom.ipc.processPriorityManager.backgroundGracePeriodMS", 1000);
 pref("dom.ipc.processPriorityManager.backgroundPerceivableGracePeriodMS", 5000);
+pref("dom.ipc.processPriorityManager.memoryPressureGracePeriodMS", 3000);
 pref("dom.ipc.processPriorityManager.temporaryPriorityLockMS", 5000);
 
 // Number of different background/foreground levels for background/foreground

dom/ipc/ProcessPriorityManager.cpp

@@ -346,6 +346,7 @@ public:
 private:
   static uint32_t sBackgroundPerceivableGracePeriodMS;
   static uint32_t sBackgroundGracePeriodMS;
+  static uint32_t sMemoryPressureGracePeriodMS;
 
   void FireTestOnlyObserverNotification(
     const char* aTopic,
@@ -370,6 +371,7 @@ private:
   nsAutoCString mNameWithComma;
 
   nsCOMPtr<nsITimer> mResetPriorityTimer;
+  nsCOMPtr<nsITimer> mMemoryPressureTimer;
 };
 
 /* static */ bool ProcessPriorityManagerImpl::sInitialized = false;
@@ -382,6 +384,7 @@ private:
   ProcessPriorityManagerImpl::sSingleton;
 /* static */ uint32_t ParticularProcessPriorityManager::sBackgroundPerceivableGracePeriodMS = 0;
 /* static */ uint32_t ParticularProcessPriorityManager::sBackgroundGracePeriodMS = 0;
+/* static */ uint32_t ParticularProcessPriorityManager::sMemoryPressureGracePeriodMS = 0;
 
 NS_IMPL_ISUPPORTS(ProcessPriorityManagerImpl,
                   nsIObserver,
@@ -701,6 +704,8 @@ ParticularProcessPriorityManager::StaticInit()
                                "dom.ipc.processPriorityManager.backgroundPerceivableGracePeriodMS");
   Preferences::AddUintVarCache(&sBackgroundGracePeriodMS,
                                "dom.ipc.processPriorityManager.backgroundGracePeriodMS");
+  Preferences::AddUintVarCache(&sMemoryPressureGracePeriodMS,
+                               "dom.ipc.processPriorityManager.memoryPressureGracePeriodMS");
 }
 
 void
@@ -1014,10 +1019,21 @@ ParticularProcessPriorityManager::ScheduleResetPriority(TimeoutPref aTimeoutPref
 NS_IMETHODIMP
 ParticularProcessPriorityManager::Notify(nsITimer* aTimer)
 {
-  LOGP("Reset priority timer callback; about to ResetPriorityNow.");
-  ResetPriorityNow();
-  mResetPriorityTimer = nullptr;
-  return NS_OK;
+  if (mResetPriorityTimer == aTimer) {
+    LOGP("Reset priority timer callback; about to ResetPriorityNow.");
+    ResetPriorityNow();
+    mResetPriorityTimer = nullptr;
+    return NS_OK;
+  }
+
+  if (mContentParent && mMemoryPressureTimer == aTimer) {
+    Unused << mContentParent->SendFlushMemory(NS_LITERAL_STRING("lowering-priority"));
+    mMemoryPressureTimer = nullptr;
+    return NS_OK;
+  }
+
+  NS_WARNING("Unexpected timer!");
+  return NS_ERROR_INVALID_POINTER;
 }
 
 bool
@@ -1142,10 +1158,18 @@ ParticularProcessPriorityManager::SetPriorityNow(ProcessPriority aPriority,
       NotifyProcessPriorityChanged(this, oldPriority);
 
     Unused << mContentParent->SendNotifyProcessPriorityChanged(mPriority);
-  }
 
-  if (aPriority < PROCESS_PRIORITY_FOREGROUND) {
-    Unused << mContentParent->SendFlushMemory(NS_LITERAL_STRING("lowering-priority"));
+    if (mMemoryPressureTimer) {
+      mMemoryPressureTimer->Cancel();
+      mMemoryPressureTimer = nullptr;
+    }
+
+    if (aPriority < PROCESS_PRIORITY_FOREGROUND) {
+      mMemoryPressureTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
+      mMemoryPressureTimer->InitWithCallback(this,
+                                             sMemoryPressureGracePeriodMS,
+                                             nsITimer::TYPE_ONE_SHOT);
+    }
   }
 
   FireTestOnlyObserverNotification("process-priority-set",