From b22bcfe208ba3574213a454245848dbe60cd15ae Mon Sep 17 00:00:00 2001
From: Cervantes Yu <cyu@mozilla.com>
Date: Thu, 13 Mar 2014 15:24:42 +0800
Subject: [PATCH] Bug 959966: prevent the preallocated process from being
 killed by the lowmem killer by rasing its priority. r=khuey,gsvelto

---
 b2g/app/b2g.js                                           | 3 +++
 .../mochitest/priority/test_Preallocated.html            | 2 +-
 dom/ipc/ContentParent.cpp                                | 4 ++--
 dom/ipc/ProcessPriorityManager.cpp                       | 4 ++++
 hal/Hal.cpp                                              | 9 +++++++++
 hal/HalTypes.h                                           | 3 +++
 hal/gonk/GonkHal.cpp                                     | 3 +++
 7 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/b2g/app/b2g.js b/b2g/app/b2g.js
index bbc464bc799..d39a51089c8 100644
--- a/b2g/app/b2g.js
+++ b/b2g/app/b2g.js
@@ -650,6 +650,9 @@ pref("hal.processPriorityManager.gonk.MASTER.OomScoreAdjust", 0);
 pref("hal.processPriorityManager.gonk.MASTER.KillUnderKB", 4096);
 pref("hal.processPriorityManager.gonk.MASTER.Nice", 0);
 
+pref("hal.processPriorityManager.gonk.PREALLOC.OomScoreAdjust", 67);
+pref("hal.processPriorityManager.gonk.PREALLOC.Nice", 18);
+
 pref("hal.processPriorityManager.gonk.FOREGROUND_HIGH.OomScoreAdjust", 67);
 pref("hal.processPriorityManager.gonk.FOREGROUND_HIGH.KillUnderKB", 5120);
 pref("hal.processPriorityManager.gonk.FOREGROUND_HIGH.Nice", 0);
diff --git a/dom/browser-element/mochitest/priority/test_Preallocated.html b/dom/browser-element/mochitest/priority/test_Preallocated.html
index f5f99683f8a..a85c481c82a 100644
--- a/dom/browser-element/mochitest/priority/test_Preallocated.html
+++ b/dom/browser-element/mochitest/priority/test_Preallocated.html
@@ -61,7 +61,7 @@ function runTest()
   // Ensure that the preallocated process initially gets BACKGROUND priority.
   // That's it.
   expectProcessCreated().then(function(childID) {
-    return expectPriorityChange(childID, 'BACKGROUND');
+    return expectPriorityChange(childID, 'PREALLOC');
   }).then(function() {
     cleanUp();
     SimpleTest.finish();
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 69aeab87de2..8b8e2124629 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -448,7 +448,7 @@ ContentParent::PreallocateAppProcess()
         new ContentParent(/* app = */ nullptr,
                           /* isForBrowserElement = */ false,
                           /* isForPreallocated = */ true,
-                          PROCESS_PRIORITY_BACKGROUND);
+                          PROCESS_PRIORITY_PREALLOC);
     process->Init();
     return process.forget();
 }
@@ -1464,7 +1464,7 @@ ContentParent::ContentParent(ContentParent* aTemplate,
     // memory priority, which it has inherited from this process.
     ProcessPriority priority;
     if (IsPreallocated()) {
-        priority = PROCESS_PRIORITY_BACKGROUND;
+        priority = PROCESS_PRIORITY_PREALLOC;
     } else {
         priority = PROCESS_PRIORITY_FOREGROUND;
     }
diff --git a/dom/ipc/ProcessPriorityManager.cpp b/dom/ipc/ProcessPriorityManager.cpp
index 5bad2420c5f..ac4633b65a9 100644
--- a/dom/ipc/ProcessPriorityManager.cpp
+++ b/dom/ipc/ProcessPriorityManager.cpp
@@ -945,6 +945,10 @@ ParticularProcessPriorityManager::ComputePriority()
 ProcessCPUPriority
 ParticularProcessPriorityManager::ComputeCPUPriority()
 {
+  if (mPriority == PROCESS_PRIORITY_PREALLOC) {
+    return PROCESS_CPU_PRIORITY_LOW;
+  }
+
   if (mPriority >= PROCESS_PRIORITY_FOREGROUND_HIGH) {
     return PROCESS_CPU_PRIORITY_NORMAL;
   }
diff --git a/hal/Hal.cpp b/hal/Hal.cpp
index ced34278fb7..f08a4e34945 100644
--- a/hal/Hal.cpp
+++ b/hal/Hal.cpp
@@ -884,6 +884,8 @@ ProcessPriorityToString(ProcessPriority aPriority)
   switch (aPriority) {
   case PROCESS_PRIORITY_MASTER:
     return "MASTER";
+  case PROCESS_PRIORITY_PREALLOC:
+    return "PREALLOC";
   case PROCESS_PRIORITY_FOREGROUND_HIGH:
     return "FOREGROUND_HIGH";
   case PROCESS_PRIORITY_FOREGROUND:
@@ -934,6 +936,13 @@ ProcessPriorityToString(ProcessPriority aPriority,
     if (aCPUPriority == PROCESS_CPU_PRIORITY_LOW) {
       return "MASTER:CPU_LOW";
     }
+  case PROCESS_PRIORITY_PREALLOC:
+    if (aCPUPriority == PROCESS_CPU_PRIORITY_NORMAL) {
+      return "PREALLOC:CPU_NORMAL";
+    }
+    if (aCPUPriority == PROCESS_CPU_PRIORITY_LOW) {
+      return "PREALLOC:CPU_LOW";
+    }
   case PROCESS_PRIORITY_FOREGROUND_HIGH:
     if (aCPUPriority == PROCESS_CPU_PRIORITY_NORMAL) {
       return "FOREGROUND_HIGH:CPU_NORMAL";
diff --git a/hal/HalTypes.h b/hal/HalTypes.h
index 271dbc64c6e..35c0c2553c7 100644
--- a/hal/HalTypes.h
+++ b/hal/HalTypes.h
@@ -84,6 +84,9 @@ enum ProcessPriority {
   PROCESS_PRIORITY_BACKGROUND_HOMESCREEN,
   PROCESS_PRIORITY_BACKGROUND_PERCEIVABLE,
   PROCESS_PRIORITY_FOREGROUND_KEYBOARD,
+  // The special class for the preallocated process, high memory priority but
+  // low CPU priority.
+  PROCESS_PRIORITY_PREALLOC,
   // Any priority greater than or equal to FOREGROUND is considered
   // "foreground" for the purposes of priority testing, for example
   // CurrentProcessIsForeground().
diff --git a/hal/gonk/GonkHal.cpp b/hal/gonk/GonkHal.cpp
index 36e91043b65..4c751926d5d 100644
--- a/hal/gonk/GonkHal.cpp
+++ b/hal/gonk/GonkHal.cpp
@@ -1258,6 +1258,9 @@ EnsureKernelLowMemKillerParamsSet()
           nsPrintfCString("hal.processPriorityManager.gonk.%s.KillUnderKB",
                           ProcessPriorityToString(priority)).get(),
           &killUnderKB))) {
+      // ProcessPriority values like PROCESS_PRIORITY_FOREGROUND_KEYBOARD,
+      // which has only OomScoreAdjust but lacks KillUnderMB value, will not
+      // create new LMK parameters.
       continue;
     }