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Commit 0c562a08 authored by Peter Kalauskas's avatar Peter Kalauskas
Browse files

Reuse coroutine trace context element 

In repeatWhenAttached, create a single coroutine trace element during
initialization, and re-use it so we allocate less objects.

Flag: ACONFIG com.android.systemui.coroutine_tracing DEVELOPMENT
Bug: 289353932
Test: SystemUITests
Change-Id: Ifb80bfcab663f35df92511fbbe94bef65e1982fe
parent dedc5fe2

packages/SystemUI/src/com/android/systemui/lifecycle/RepeatWhenAttached.kt

+15 −5
Original line number Diff line number Diff line
@@ -70,8 +70,7 @@ fun View.repeatWhenAttached( 
    // dispatcher to use. We don't want it to run on the Dispatchers.Default thread pool as

    // default behavior. Instead, we want it to run on the view's UI thread since the user will

    // presumably want to call view methods that require being called from said UI thread.

    val lifecycleCoroutineContext =

        Dispatchers.Main + createCoroutineTracingContext() + coroutineContext

    val lifecycleCoroutineContext = MAIN_DISPATCHER_SINGLETON + coroutineContext

    val traceName =

        if (Compile.IS_DEBUG && coroutineTracing()) {

            inferTraceSectionName()
@@ -205,17 +204,28 @@ private fun inferTraceSectionName(): String { 
            StackWalker.getInstance().walk { stream ->

                stream.filter(::isFrameInteresting).limit(5).findFirst()

            }

        if (interestingFrame.isPresent) {

        return if (interestingFrame.isPresent) {

            val f = interestingFrame.get()

            return "${f.className}#${f.methodName}:${f.lineNumber} [$DEFAULT_TRACE_NAME]"

            "${f.className}#${f.methodName}:${f.lineNumber} [$DEFAULT_TRACE_NAME]"

        } else {

            return DEFAULT_TRACE_NAME

            DEFAULT_TRACE_NAME

        }

    } finally {

        Trace.traceEnd(Trace.TRACE_TAG_APP)

    }

}



/**

 * Even though there is only has one usage of `Dispatchers.Main` in this file, we cache it in a

 * top-level property so that we do not unnecessarily create new `CoroutineContext` objects for

 * tracing on each call to [repeatWhenAttached]. It is okay to reuse a single instance of the

 * tracing context because it is copied for its children.

 *

 * Also, ideally, we would use the injected `@Main CoroutineDispatcher`, but [repeatWhenAttached] is

 * an extension function, and plumbing dagger-injected instances for static usage has little

 * benefit.

 */

private val MAIN_DISPATCHER_SINGLETON = Dispatchers.Main + createCoroutineTracingContext()

private const val DEFAULT_TRACE_NAME = "repeatWhenAttached"

private const val CURRENT_CLASS_NAME = "com.android.systemui.lifecycle.RepeatWhenAttachedKt"

private const val JAVA_ADAPTER_CLASS_NAME = "com.android.systemui.util.kotlin.JavaAdapterKt"