47 lines
2.0 KiB
Kotlin
47 lines
2.0 KiB
Kotlin
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mozilla.fenix.perf
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import android.os.SystemClock
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import android.util.Log
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/**
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* Monitors and reports elapsed time to complete hot startup of an Activity. Callers are expected
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* to call the appropriate lifecycle methods at the appropriate times.
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*
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* A "hot startup" is when the application moves from the background to the foreground and both the
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* Application/process and the Activity under measurement are already created.
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*
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* Unfortunately, this monitor does not capture the entire duration of hot start because the
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* framework calls several Android framework methods in the application's process before we are able
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* to add monitoring code (i.e. the first time our application code is called in onRestart). An
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* alternative implementation could measure performance from outside the application.
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*
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* The logs from this class are not visible to users by default. To see logs from this class, the
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* user must enable VERBOSE logging for the appropriate tag:
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* adb shell setprop log.tag.FenixPerf VERBOSE
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*/
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class HotStartPerformanceMonitor(
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// We use VERBOSE logging so that the logs are not visible to users by default. We use the
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// Android Log methods to minimize overhead introduced in a-c logging.
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private val log: (String) -> Unit = { Log.v(Performance.TAG, it) },
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private val getElapsedRealtime: () -> Long = { SystemClock.elapsedRealtime() }
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) {
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private var onRestartMillis: Long = -1
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fun onRestartFirstMethodCall() {
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onRestartMillis = getElapsedRealtime()
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}
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fun onPostResumeFinalMethodCall() {
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// If onRestart was never called, this is not a hot start: ignore it.
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if (onRestartMillis >= 0) {
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val elapsedMillis = getElapsedRealtime() - onRestartMillis
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log("hot start: $elapsedMillis")
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}
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}
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}
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