Activity Manager changes the scheduling group of processes.

The algorithm for this is currently very simple: all persistent processes are
always in the normal scheduling group, all other processes are normal if their
oom_adj is as good or better than VISIBLE, otherwise they are in the background
group.

Note that this currently results in a fair number of log messages about not
being able to change the group, since the system process does not have
permission to do so.  Once a kernel fix is in, these will go away and the code
will start working.

core/java/android/app/ActivityThread.java

@@ -1513,6 +1513,18 @@ public final class ActivityThread {
             queueOrSendMessage(H.PROFILER_CONTROL, path, start ? 1 : 0);
         }
 
+        public void setSchedulingGroup(int group) {
+            // Note: do this immediately, since going into the foreground
+            // should happen regardless of what pending work we have to do
+            // and the activity manager will wait for us to report back that
+            // we are done before sending us to the background.
+            try {
+                Process.setProcessGroup(Process.myPid(), group);
+            } catch (Exception e) {
+                Log.w(TAG, "Failed setting process group to " + group, e);
+            }
+        }
+        
         @Override
         protected void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
             long nativeMax = Debug.getNativeHeapSize() / 1024;

core/java/android/app/ApplicationThreadNative.java

@@ -331,6 +331,14 @@ public abstract class ApplicationThreadNative extends Binder
             profilerControl(start, path);
             return true;
         }
+        
+        case SET_SCHEDULING_GROUP_TRANSACTION:
+        {
+            data.enforceInterface(IApplicationThread.descriptor);
+            int group = data.readInt();
+            setSchedulingGroup(group);
+            return true;
+        }
         }
 
         return super.onTransact(code, data, reply, flags);
@@ -672,5 +680,14 @@ class ApplicationThreadProxy implements IApplicationThread {
                 IBinder.FLAG_ONEWAY);
         data.recycle();
     }
+    
+    public void setSchedulingGroup(int group) throws RemoteException {
+        Parcel data = Parcel.obtain();
+        data.writeInterfaceToken(IApplicationThread.descriptor);
+        data.writeInt(group);
+        mRemote.transact(SET_SCHEDULING_GROUP_TRANSACTION, data, null,
+                IBinder.FLAG_ONEWAY);
+        data.recycle();
+    }
 }
 

core/java/android/app/IApplicationThread.java

@@ -87,7 +87,8 @@ public interface IApplicationThread extends IInterface {
     void scheduleActivityConfigurationChanged(IBinder token) throws RemoteException;
     void requestPss() throws RemoteException;
     void profilerControl(boolean start, String path) throws RemoteException;
-
+    void setSchedulingGroup(int group) throws RemoteException;
+    
     String descriptor = "android.app.IApplicationThread";
 
     int SCHEDULE_PAUSE_ACTIVITY_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION;
@@ -117,4 +118,5 @@ public interface IApplicationThread extends IInterface {
     int SCHEDULE_RELAUNCH_ACTIVITY_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+25;
     int REQUEST_PSS_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+26;
     int PROFILER_CONTROL_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+27;
+    int SET_SCHEDULING_GROUP_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+28;
 }

services/java/com/android/server/am/ActivityManagerService.java

@@ -4733,6 +4733,7 @@ public final class ActivityManagerService extends ActivityManagerNative implemen
         
         app.thread = thread;
         app.curAdj = app.setAdj = -100;
+        app.curSchedGroup = app.setSchedGroup = Process.THREAD_GROUP_DEFAULT;
         app.forcingToForeground = null;
         app.foregroundServices = false;
         app.debugging = false;
@@ -8802,9 +8803,9 @@ public final class ActivityManagerService extends ActivityManagerNative implemen
                       + " #" + i + ":");
                 r.dump(pw, prefix + "  ");
             } else if (inclOomAdj) {
-                pw.println(String.format("%s%s #%2d: oom_adj=%3d %s",
+                pw.println(String.format("%s%s #%2d: adj=%3d/%d %s",
                         prefix, (r.persistent ? persistentLabel : normalLabel),
-                        i, r.setAdj, r.toString()));
+                        i, r.setAdj, r.setSchedGroup, r.toString()));
             } else {
                 pw.println(String.format("%s%s #%2d: %s",
                         prefix, (r.persistent ? persistentLabel : normalLabel),
@@ -11830,7 +11831,10 @@ public final class ActivityManagerService extends ActivityManagerNative implemen
         }
 
         app.curAdj = adj;
-
+        app.curSchedGroup = (adj > VISIBLE_APP_ADJ && !app.persistent)
+                ? Process.THREAD_GROUP_BG_NONINTERACTIVE
+                : Process.THREAD_GROUP_DEFAULT;
+        
         return adj;
     }
 
@@ -11975,6 +11979,28 @@ public final class ActivityManagerService extends ActivityManagerNative implemen
                     return false;
                 }
             }
+            if (app.setSchedGroup != app.curSchedGroup) {
+                app.setSchedGroup = app.curSchedGroup;
+                if (DEBUG_SWITCH || DEBUG_OOM_ADJ) Log.v(TAG,
+                        "Setting process group of " + app.processName
+                        + " to " + app.curSchedGroup);
+                if (true) {
+                    try {
+                        Process.setProcessGroup(app.pid, app.curSchedGroup);
+                    } catch (Exception e) {
+                        Log.w(TAG, "Failed setting process group of " + app.pid
+                                + " to " + app.curSchedGroup);
+                    }
+                }
+                if (false) {
+                    if (app.thread != null) {
+                        try {
+                            app.thread.setSchedulingGroup(app.curSchedGroup);
+                        } catch (RemoteException e) {
+                        }
+                    }
+                }
+            }
         }
 
         return true;

services/java/com/android/server/am/ProcessRecord.java

@@ -56,6 +56,8 @@ class ProcessRecord implements Watchdog.PssRequestor {
     int setRawAdj;              // Last set OOM unlimited adjustment for this process
     int curAdj;                 // Current OOM adjustment for this process
     int setAdj;                 // Last set OOM adjustment for this process
+    int curSchedGroup;          // Currently desired scheduling class
+    int setSchedGroup;          // Last set to background scheduling class
     boolean isForeground;       // Is this app running the foreground UI?
     boolean setIsForeground;    // Running foreground UI when last set?
     boolean foregroundServices; // Running any services that are foreground?
@@ -147,6 +149,8 @@ class ProcessRecord implements Watchdog.PssRequestor {
                 pw.print(" setRaw="); pw.print(setRawAdj);
                 pw.print(" cur="); pw.print(curAdj);
                 pw.print(" set="); pw.println(setAdj);
+        pw.print(prefix); pw.print("curSchedGroup="); pw.print(curSchedGroup);
+                pw.print(" setSchedGroup="); pw.println(setSchedGroup);
         pw.print(prefix); pw.print("isForeground="); pw.print(isForeground);
                 pw.print(" setIsForeground="); pw.print(setIsForeground);
                 pw.print(" foregroundServices="); pw.print(foregroundServices);