commit 6eee56ccabd89adb56edf45db587ef4db7c68722
author Tim Murray <timmurray@google.com> Tue Nov 10 14:31:09 2015 -0800
committer Justin Harrison <astyrrian@google.com> Wed Nov 18 22:36:23 2015 +0000
tree 73ef10d0f5dec84329663d19c6073b9c39c7b772
parent 1589fa1bda5d8e990c0a0f9a72841b8fa52899ed

Improve cpuset support for surfaceflinger.

SurfaceFlinger needs some of its threads in the system-background cpuset
and some of its threads (the binder pool) outside of the
system-background cpuset in order to improve UI perf/power
consumption. Remove surfaceflinger from the system-background cpuset in
init.rc and allow a thread to place itself in the system-background
cpuset given enough permissions.

bug 25745866

Change-Id: I85f7e41c5439e6ad7cc2d355e51f5dfb3a0c7088

libcutils/sched_policy.c

diff --git a/libcutils/sched_policy.c b/libcutils/sched_policy.c
index 83222f4..8c26cdd 100644
--- a/libcutils/sched_policy.c
+++ b/libcutils/sched_policy.c
@@ -61,6 +61,7 @@
 static int fg_cgroup_fd = -1;
 
 // File descriptors open to /dev/cpuset/../tasks, setup by initialize, or -1 on error
+static int system_bg_cpuset_fd = -1;
 static int bg_cpuset_fd = -1;
 static int fg_cpuset_fd = -1;
 
@@ -126,6 +127,11 @@
         fg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
         filename = "/dev/cpuset/background/tasks";
         bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+        filename = "/dev/cpuset/system-background/tasks";
+        system_bg_cpuset_fd = open(filename, O_WRONLY | O_CLOEXEC);
+        if (system_bg_cpuset_fd < 0) {
+            SLOGE("initialize of system-bg failed: %s\n", strerror(errno));
+        }
     }
 #endif
 
@@ -260,6 +266,9 @@
     case SP_AUDIO_SYS:
         fd = fg_cpuset_fd;
         break;
+    case SP_SYSTEM:
+        fd = system_bg_cpuset_fd;
+        break;
     default:
         fd = -1;
         break;

rootdir/init.rc

diff --git a/rootdir/init.rc b/rootdir/init.rc
index 317207c..4cc3f73 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -165,13 +165,19 @@
     chown system system /dev/cpuset/foreground
     chown system system /dev/cpuset/foreground/boost
     chown system system /dev/cpuset/background
+    chown system system /dev/cpuset/system-background
     chown system system /dev/cpuset/tasks
     chown system system /dev/cpuset/foreground/tasks
     chown system system /dev/cpuset/foreground/boost/tasks
     chown system system /dev/cpuset/background/tasks
+    chown system system /dev/cpuset/system-background/tasks
+
+    # set system-background to 0775 so SurfaceFlinger can touch it
+    chmod 0775 /dev/cpuset/system-background
     chmod 0664 /dev/cpuset/foreground/tasks
     chmod 0664 /dev/cpuset/foreground/boost/tasks
     chmod 0664 /dev/cpuset/background/tasks
+    chmod 0664 /dev/cpuset/system-background/tasks
     chmod 0664 /dev/cpuset/tasks
 
 
@@ -646,7 +652,6 @@
     user system
     group graphics drmrpc
     onrestart restart zygote
-    writepid /dev/cpuset/system-background/tasks
 
 service drm /system/bin/drmserver
     class main