Cleanup and consistency around system server profiling.

The profiling currently works by accident: only because we profile the
boot classpath which executes in JIT zygote do we not load system server
AOT artifacts.

So make the not loading AOT artifacts in system server explicit when the
system server is being profild.

Test: system server profiling
Change-Id: I8d787c8f8524d9d6074dc0f552a856640f11cef0

core/java/com/android/internal/os/SystemServerClassLoaderFactory.java

@@ -87,6 +87,10 @@ public final class SystemServerClassLoaderFactory {
         if (isTestOnly) {
             return true;
         }
+        // If system server is being profiled, it's OK to create class loaders anytime.
+        if (ZygoteInit.shouldProfileSystemServer()) {
+            return true;
+        }
         return false;
     }
 

core/java/com/android/internal/os/ZygoteInit.java

@@ -238,6 +238,21 @@ public class ZygoteInit {
         Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
     }
 
+    private static boolean isExperimentEnabled(String experiment) {
+        boolean defaultValue = SystemProperties.getBoolean(
+                "dalvik.vm." + experiment,
+                /*def=*/false);
+        // Can't use device_config since we are the zygote, and it's not initialized at this point.
+        return SystemProperties.getBoolean(
+                "persist.device_config." + DeviceConfig.NAMESPACE_RUNTIME_NATIVE_BOOT
+                        + "." + experiment,
+                defaultValue);
+    }
+
+    /* package-private */ static boolean shouldProfileSystemServer() {
+        return isExperimentEnabled("profilesystemserver");
+    }
+
     /**
      * Performs Zygote process initialization. Loads and initializes commonly used classes.
      *
@@ -341,14 +356,7 @@ public class ZygoteInit {
             // If we are profiling the boot image, reset the Jit counters after preloading the
             // classes. We want to preload for performance, and we can use method counters to
             // infer what clases are used after calling resetJitCounters, for profile purposes.
-            // Can't use device_config since we are the zygote.
-            String prop = SystemProperties.get(
-                    "persist.device_config.runtime_native_boot.profilebootclasspath", "");
-            // Might be empty if the property is unset since the default is "".
-            if (prop.length() == 0) {
-                prop = SystemProperties.get("dalvik.vm.profilebootclasspath", "");
-            }
-            if ("true".equals(prop)) {
+            if (isExperimentEnabled("profilebootclasspath")) {
                 Trace.traceBegin(Trace.TRACE_TAG_DALVIK, "ResetJitCounters");
                 VMRuntime.resetJitCounters();
                 Trace.traceEnd(Trace.TRACE_TAG_DALVIK);
@@ -489,16 +497,6 @@ public class ZygoteInit {
         ZygoteHooks.gcAndFinalize();
     }
 
-    private static boolean shouldProfileSystemServer() {
-        boolean defaultValue = SystemProperties.getBoolean("dalvik.vm.profilesystemserver",
-                /*default=*/ false);
-        // Can't use DeviceConfig since it's not initialized at this point.
-        return SystemProperties.getBoolean(
-                "persist.device_config." + DeviceConfig.NAMESPACE_RUNTIME_NATIVE_BOOT
-                        + ".profilesystemserver",
-                defaultValue);
-    }
-
     /**
      * Finish remaining work for the newly forked system server process.
      */
@@ -580,6 +578,13 @@ public class ZygoteInit {
      * in the forked system server process in the zygote SELinux domain.
      */
     private static void prefetchStandaloneSystemServerJars() {
+        if (shouldProfileSystemServer()) {
+            // We don't prefetch AOT artifacts if we are profiling system server, as we are going to
+            // JIT it.
+            // This method only gets called from native and should already be skipped if we profile
+            // system server. Still, be robust and check it again.
+            return;
+        }
         String envStr = Os.getenv("STANDALONE_SYSTEMSERVER_JARS");
         if (TextUtils.isEmpty(envStr)) {
             return;

core/jni/com_android_internal_os_Zygote.cpp

@@ -343,6 +343,7 @@ enum MountExternalKind {
 // Must match values in com.android.internal.os.Zygote.
 enum RuntimeFlags : uint32_t {
     DEBUG_ENABLE_JDWP = 1,
+    PROFILE_SYSTEM_SERVER = 1 << 14,
     PROFILE_FROM_SHELL = 1 << 15,
     MEMORY_TAG_LEVEL_MASK = (1 << 19) | (1 << 20),
     MEMORY_TAG_LEVEL_TBI = 1 << 19,
@@ -1634,9 +1635,11 @@ static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
                                            instruction_set.value().c_str());
     }
 
-    if (is_system_server) {
+    if (is_system_server && !(runtime_flags & RuntimeFlags::PROFILE_SYSTEM_SERVER)) {
         // Prefetch the classloader for the system server. This is done early to
         // allow a tie-down of the proper system server selinux domain.
+        // We don't prefetch when the system server is being profiled to avoid
+        // loading AOT code.
         env->CallStaticObjectMethod(gZygoteInitClass, gGetOrCreateSystemServerClassLoader);
         if (env->ExceptionCheck()) {
             // Be robust here. The Java code will attempt to create the classloader