Set android.display thread to top-app cpusets and schedtune group

android.display being in the foreground cpuset group is an issue. As
seen on M/S, during heavily CPU load it is not given core 3 even though
it might be free and causes jank. This patch adds the thread to the
top-app group to ensure it is placed on all cores during scheduling
decisions.

Doing this required a couple of changes:
- new API to set per-thread cpusets
- changes to DisplayManagerService to set the thread to top-app group
- changes to SystemServer to set the policy toward the end, as doing it
  during start of the DisplayManagerService was in issue (issue being
  SystemServer calls setSystemProcess.. -> setProcessGroup which overrides
  the group settings for threads in the system server process, including
  android.display)

Bug: 36631902
Test: Boot and make sure android.display thread is in the top-app group

Change-Id: Icc394ea0ffcf159d11728ad38de114234a29d20f
Signed-off-by: Joel Fernandes <joelaf@google.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index 31376587e144..7a709ed59b15 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -660,7 +660,7 @@ public class Process {
      * @hide
      * @param tid The identifier of the thread to change.
      * @param group The target group for this thread from THREAD_GROUP_*.
-     * 
+     *
      * @throws IllegalArgumentException Throws IllegalArgumentException if
      * <var>tid</var> does not exist.
      * @throws SecurityException Throws SecurityException if your process does
@@ -676,6 +676,21 @@ public class Process {
             throws IllegalArgumentException, SecurityException;
 
     /**
+     * Sets the scheduling group and the corresponding cpuset group
+     * @hide
+     * @param tid The identifier of the thread to change.
+     * @param group The target group for this thread from THREAD_GROUP_*.
+     *
+     * @throws IllegalArgumentException Throws IllegalArgumentException if
+     * <var>tid</var> does not exist.
+     * @throws SecurityException Throws SecurityException if your process does
+     * not have permission to modify the given thread, or to use the given
+     * priority.
+     */
+    public static final native void setThreadGroupAndCpuset(int tid, int group)
+            throws IllegalArgumentException, SecurityException;
+
+    /**
      * Sets the scheduling group for a process and all child threads
      * @hide
      * @param pid The identifier of the process to change.