ThrottleDetector.kt
/*
* Copyright 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.benchmark
import android.content.Context
import android.opengl.Matrix
import android.os.Build
import android.os.PowerManager
import androidx.annotation.RequiresApi
import androidx.test.platform.app.InstrumentationRegistry
internal object ThrottleDetector {
private var initNs = 0.0
/**
* Copies 400K, 10 times.
*/
private fun copySomeData() {
val a = ByteArray(400_000)
val b = ByteArray(400_000)
repeat(10) {
System.arraycopy(a, 0, b, 0, a.size)
}
}
internal fun measureWorkNs(): Double {
// Access a non-trivial amount of data to try and 'reset' any cache state.
// Have observed this to give more consistent performance when clocks are unlocked.
copySomeData()
val state = BenchmarkState(simplifiedTimingOnlyMode = true)
val sourceMatrix = FloatArray(16) { System.nanoTime().toFloat() }
val resultMatrix = FloatArray(16)
while (state.keepRunningInline()) {
// Benchmark a simple thermal
Matrix.translateM(resultMatrix, 0, sourceMatrix, 0, 1F, 2F, 3F)
}
return state.getMinTimeNanos()
}
/**
* Called to calculate throttling baseline, will be ignored after first call until reset.
*
* Does nothing if baseline isn't needed
*/
fun computeThrottleBaselineIfNeeded() {
if (Build.VERSION.SDK_INT < 29 && // can't use PowerManager API yet
initNs == 0.0 && // first time
!CpuInfo.locked && // CPU locked (presumably to stable values), should be no throttling
!IsolationActivity.sustainedPerformanceModeInUse && // trust sustained perf
!Errors.isEmulator // don't bother with emulators, will always be unpredicatable
) {
initNs = measureWorkNs()
}
}
/**
* Called to reset throttle baseline, if throttle detection is firing too regularly, and
* inaccurate initial measurement is suspected.
*/
fun resetThrottleBaseline() {
initNs = 0.0
}
/**
* Makes a guess as to whether the device is currently thermal throttled based on performance
* of single-threaded CPU work.
*/
fun isDeviceThermalThrottled(): Boolean {
if (Build.VERSION.SDK_INT >= 29) {
return Api29Helper.isDeviceThermalThrottled()
}
if (initNs == 0.0) {
// baseline not set, so assume not throttled.
return false
}
val workNs = measureWorkNs()
return workNs > initNs * 1.10
}
@RequiresApi(29)
internal object Api29Helper {
/**
* We don't accept any thermal throttling status over NONE, since we have observed
* significant CPU variation even with `THERMAL_STATUS_LIGHT` (see ThrottleDetectorTest).
*
* On a Pixel 2 running API 30, we've seen variation from 55 - 72ms in the measureWorkNs()
* matrix workload.
*/
fun isDeviceThermalThrottled(): Boolean {
return (InstrumentationRegistry
.getInstrumentation()
.context
.getSystemService(Context.POWER_SERVICE) as PowerManager)
.currentThermalStatus > PowerManager.THERMAL_STATUS_NONE
}
}
}