Bug 980027 - Part 3: Add compositor priority prefs to b2g.js. r=gsvelto

b2g/app/b2g.js

@@ -689,6 +689,19 @@ pref("hal.processPriorityManager.gonk.BACKGROUND.Nice", 18);
 // Processes get this niceness when they have low CPU priority.
 pref("hal.processPriorityManager.gonk.LowCPUNice", 18);
 
+// By default the compositor thread on gonk runs without real-time priority.  RT
+// priority can be enabled by setting this pref to a value between 1 and 99.
+// Note that audio processing currently runs at RT priority 2 or 3 at most.
+//
+// If RT priority is disabled, then the compositor nice value is used.  The
+// code will default to ANDROID_PRIORITY_URGENT_DISPLAY which is -8.  Per gfx
+// request we are keeping the compositor at nice level 0 until we can complete
+// the investigation in bug 982972.
+//
+// Do not change these values without gfx team review.
+pref("hal.gonk.COMPOSITOR.rt_priority", 0);
+pref("hal.gonk.COMPOSITOR.nice", 0);
+
 // Fire a memory pressure event when the system has less than Xmb of memory
 // remaining.  You should probably set this just above Y.KillUnderKB for
 // the highest priority class Y that you want to make an effort to keep alive.