Trace: Disable debug tracing on production builds

When opening and closing activities in Settings, a significant amount of
CPU time is spent checking whether ATrace tags are enabled, as measured
by simpleperf:

0.12%     /system/lib64/libcutils.so                                                                                                                atrace_get_enabled_tag

android.os.Trace is responsible for a significant portion of the time
spent in the checks:

0.10%     0.07%  /system/lib64/libcutils.so                                                                                              atrace_get_enabled_tags
       |
       -- atrace_get_enabled_tags
          |
          |
          |--1.62%-- android.os.Trace.traceEnd
          |    |--36.90%-- [hit in function]
          |    |
          |    |--29.76%-- android.view.Choreographer.doCallbacks
          |    |           android.view.Choreographer.doFrame
          |    |           android.view.Choreographer$FrameDisplayEventReceiver.run
          |    |           android.os.Handler.dispatchMessage
          |    |           android.os.Looper.loop
          |    |           android.os.HandlerThread.run
          |    |           com.android.server.ServiceThread.run
          |    |           art_quick_invoke_stub
          |    |           art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)
          |    |           art::JValue art::InvokeVirtualOrInterfaceWithJValues<art::ArtMethod*>(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, art::ArtMethod*, jvalue const*)
          |    |           art::Thread::CreateCallback(void*)
          |    |           __pthread_start(void*)
          |    |           __start_thread
          |    |
          |    |--19.00%-- com.android.server.BatteryService$BatteryPropertiesRegistrar.getProperty
          |    |           android.os.IBatteryPropertiesRegistrar$Stub.onTransact
          |    |           android.os.Binder.execTransactInternal
          |    |           android.os.Binder.execTransact
          |    |           art_quick_invoke_stub
          |    |           art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)
          |    |           art::JValue art::InvokeVirtualOrInterfaceWithVarArgs<art::ArtMethod*>(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, art::ArtMethod*, std::__va_list)
          |    |           art::JValue art::InvokeVirtualOrInterfaceWithVarArgs<_jmethodID*>(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, _jmethodID*, std::__va_list)
          |    |           art::JNI<false>::CallBooleanMethodV(_JNIEnv*, _jobject*, _jmethodID*, std::__va_list)
          |    |           _JNIEnv::CallBooleanMethod(_jobject*, _jmethodID*, ...)
          |    |           JavaBBinder::onTransact(unsigned int, android::Parcel const&, android::Parcel*, unsigned int)
          |    |           android::BBinder::transact(unsigned int, android::Parcel const&, android::Parcel*, unsigned int)
          |    |           android::IPCThreadState::executeCommand(int)
          |    |           android::IPCThreadState::getAndExecuteCommand()
          |    |           android::IPCThreadState::joinThreadPool(bool)
          |    |           android::PoolThread::threadLoop()
          |    |           android::Thread::_threadLoop(void*)
          |    |           android::AndroidRuntime::javaThreadShell(void*)
          |    |           thread_data_t::trampoline(thread_data_t const*)
          |    |           __pthread_start(void*)
          |    |           __start_thread
          |    |
          |     --14.33%-- android.view.ViewRootImpl.performDraw
          |                android.view.ViewRootImpl.performTraversals
          |                android.view.ViewRootImpl.doTraversal
          |                android.content.ContextWrapper.getAssets [DEDUPED]
          |                android.view.Choreographer.doCallbacks
          |                android.view.Choreographer.doFrame
          |                android.view.Choreographer$FrameDisplayEventReceiver.run
          |                android.os.Handler.dispatchMessage
          |                android.os.Looper.loop
          |                android.app.ActivityThread.main
          |                art_quick_invoke_static_stub
          |                art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)
          |                art::InvokeMethod(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, _jobject*, _jobject*, unsigned long)
          |                art::Method_invoke(_JNIEnv*, _jobject*, _jobject*, _jobjectArray*)
          |                art_jni_trampoline
          |                com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run
          |                com.android.internal.os.ZygoteInit.main
          |                art_quick_invoke_static_stub
          |                art::ArtMethod::Invoke(art::Thread*, unsigned int*, unsigned int, art::JValue*, char const*)
          |                art::JValue art::InvokeWithVarArgs<art::ArtMethod*>(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, art::ArtMethod*, std::__va_list)
          |                art::JValue art::InvokeWithVarArgs<_jmethodID*>(art::ScopedObjectAccessAlreadyRunnable const&, _jobject*, _jmethodID*, std::__va_list)
          |                art::JNI<true>::CallStaticVoidMethodV(_JNIEnv*, _jclass*, _jmethodID*, std::__va_list)
          |                _JNIEnv::CallStaticVoidMethod(_jclass*, _jmethodID*, ...)
          |                android::AndroidRuntime::start(char const*, android::Vector<android::String8> const&, bool)
          |                main
          |                __libc_init

We're unlikely to trace the system and framework in production systems,
so disable debug tracing in non-debuggable builds. The ro.debuggable
check is performed from the Java side for simplicity.

Test: simpleperf record -a; verify that android.os.Trace no longer
      appears under atrace_get_enabled_tags
Change-Id: I9b63d386c041ffd9d7ff34ecd0ec1eb95dc03b4b

1 files changed, 4 insertions, 0 deletions

diff --git a/core/java/android/os/Trace.java b/core/java/android/os/Trace.java
index ddb6533547bb..85fad2833e81 100644
--- a/core/java/android/os/Trace.java
+++ b/core/java/android/os/Trace.java
@@ -145,6 +145,10 @@ public final class Trace {
      */
     @UnsupportedAppUsage
     public static boolean isTagEnabled(long traceTag) {
+        if (!Build.IS_DEBUGGABLE) {
+            return false;
+        }
+
         long tags = nativeGetEnabledTags();
         return (tags & traceTag) != 0;
     }