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

1 files changed, 8 insertions, 1 deletions

diff --git a/libcutils/sched_policy.c b/libcutils/sched_policy.c
index 6bba3a7b1..280a0834b 100644
--- a/libcutils/sched_policy.c
+++ b/libcutils/sched_policy.c
@@ -62,6 +62,7 @@ static int fg_cgroup_fd = -1;
 
 #ifdef USE_CPUSETS
 // 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;
 static int bg_schedboost_fd = -1;
@@ -130,6 +131,9 @@ static void __initialize(void) {
         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);
+
 #ifdef USE_SCHEDBOOST
         filename = "/sys/fs/cgroup/stune/foreground/tasks";
         fg_schedboost_fd = open(filename, O_WRONLY | O_CLOEXEC);
@@ -138,7 +142,6 @@ static void __initialize(void) {
 #endif
     }
 #endif
-
 }
 
 /*
@@ -273,6 +276,10 @@ int set_cpuset_policy(int tid, SchedPolicy policy)
         fd = fg_cpuset_fd;
         boost_fd = fg_schedboost_fd;
         break;
+    case SP_SYSTEM:
+        fd = system_bg_cpuset_fd;
+        boost_fd = bg_schedboost_fd;
+        break;
     default:
         boost_fd = fd = -1;
         break;