am ffd8889a: am f76806a9: Merge "Add boost to increase the load on newly-forked zygote processes." into mnc-dr-dev

* commit 'ffd8889a96db0dadf01f6dfcd9393910d491fb91':
  Add boost to increase the load on newly-forked zygote processes.

core/jni/Android.mk

@@ -20,6 +20,10 @@ ifneq ($(ENABLE_CPUSETS),)
     LOCAL_CFLAGS += -DENABLE_CPUSETS
 endif
 
+ifneq ($(ENABLE_SCHED_BOOST),)
+    LOCAL_CFLAGS += -DENABLE_SCHED_BOOST
+endif
+
 LOCAL_CFLAGS += -DGL_GLEXT_PROTOTYPES -DEGL_EGLEXT_PROTOTYPES
 
 LOCAL_CFLAGS += -DU_USING_ICU_NAMESPACE=0

core/jni/com_android_internal_os_Zygote.cpp

@@ -408,6 +408,27 @@ void SetThreadName(const char* thread_name) {
   }
 }
 
+#ifdef ENABLE_SCHED_BOOST
+static void SetForkLoad(bool boost) {
+  // set scheduler knob to boost forked processes
+  pid_t currentPid = getpid();
+  // fits at most "/proc/XXXXXXX/sched_init_task_load\0"
+  char schedPath[35];
+  snprintf(schedPath, sizeof(schedPath), "/proc/%u/sched_init_task_load", currentPid);
+  int schedBoostFile = open(schedPath, O_WRONLY);
+  if (schedBoostFile < 0) {
+    ALOGW("Unable to set zygote scheduler boost");
+    return;
+  }
+  if (boost) {
+    write(schedBoostFile, "100\0", 4);
+  } else {
+    write(schedBoostFile, "0\0", 2);
+  }
+  close(schedBoostFile);
+}
+#endif
+
 // Utility routine to fork zygote and specialize the child process.
 static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids,
                                      jint debug_flags, jobjectArray javaRlimits,
@@ -418,6 +439,10 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
                                      jstring instructionSet, jstring dataDir) {
   SetSigChldHandler();
 
+#ifdef ENABLE_SCHED_BOOST
+  SetForkLoad(true);
+#endif
+
   pid_t pid = fork();
 
   if (pid == 0) {
@@ -558,6 +583,12 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
     }
   } else if (pid > 0) {
     // the parent process
+
+#ifdef ENABLE_SCHED_BOOST
+    // unset scheduler knob
+    SetForkLoad(false);
+#endif
+
   }
   return pid;
 }