Increase priority of raster threads on Android.

base/threading/platform_thread_android.cc

 // 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.
 
 #include "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <sys/prctl.h>
 #include <sys/resource.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "base/android/jni_android.h"
 #include "base/android/thread_utils.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/threading/platform_thread_internal_posix.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/tracked_objects.h"
 #include "jni/ThreadUtils_jni.h"
 
 namespace base {
 
 namespace internal {
 
-// These nice values are taken from Android, which uses nice values like linux,
-// but defines some preset nice values.
-//   Process.THREAD_PRIORITY_AUDIO = -16
-//   Process.THREAD_PRIORITY_BACKGROUND = 10
-//   Process.THREAD_PRIORITY_DEFAULT = 0;
-//   Process.THREAD_PRIORITY_DISPLAY = -4;
-//   Process.THREAD_PRIORITY_FOREGROUND = -2;
-//   Process.THREAD_PRIORITY_LESS_FAVORABLE = 1;
-//   Process.THREAD_PRIORITY_LOWEST = 19;
-//   Process.THREAD_PRIORITY_MORE_FAVORABLE = -1;
-//   Process.THREAD_PRIORITY_URGENT_AUDIO = -19;
-//   Process.THREAD_PRIORITY_URGENT_DISPLAY = -8;
-// We use -6 for display, but we may want to split this into urgent (-8) and
-// non-urgent (-4).
+// - BACKGROUND is 9 due to it being the nicest value we can use that's still

[danakj, 2015/07/06 23:24:22]

Thanks this comment is awesome.

+// above an Android system threshold that enables heavy throttling starting at
+// 10; we want to be lower-priority than Chrome's other threads without
+// incurring this behavior.
+// - DISPLAY is -6 due to being midway between Android's DISPLAY (-4) and
+// URGENT_DISPLAY (-8).
+// - REALTIME_AUDIO corresponds to Android's THREAD_PRIORITY_AUDIO = -16 value.
 const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
-    {ThreadPriority::BACKGROUND, 10},
+    {ThreadPriority::BACKGROUND, 9},
     {ThreadPriority::NORMAL, 0},
     {ThreadPriority::DISPLAY, -6},
     {ThreadPriority::REALTIME_AUDIO, -16},
 };
 
 bool SetThreadPriorityForPlatform(PlatformThreadHandle handle,
                                   ThreadPriority priority) {
   // On Android, we set the Audio priority through JNI as Audio priority
   // will also allow the process to run while it is backgrounded.
   if (priority == ThreadPriority::REALTIME_AUDIO) {
@@ skipping 52 matching lines @@
   // 1Mb is not enough for some tests (see http://crbug.com/263749 for example).
   return 2 * (1 << 20);  // 2Mb
 #endif
 }
 
 bool RegisterThreadUtils(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace base