Perf test to measure various mechanisms to track CPU.

/*

 * Copyright (C) 2018 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 android.os;

import android.perftests.utils.BenchmarkState;

import android.perftests.utils.PerfStatusReporter;

import android.support.test.filters.LargeTest;

import android.support.test.runner.AndroidJUnit4;

import org.junit.Rule;

import org.junit.Test;

import org.junit.runner.RunWith;

import java.nio.file.Files;

import java.nio.file.Paths;

/**

 * Performance tests collecting CPU data different mechanisms.

 */

@RunWith(AndroidJUnit4.class)

@LargeTest

public class CpuUsageTrackingPerfTest {

    @Rule

    public PerfStatusReporter mPerfStatusReporter = new PerfStatusReporter();

    @Test

    public void timeSystemThread() {

        final BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        Binder b = new Binder();

        while (state.keepRunning()) {

            SystemClock.currentThreadTimeMicro();

        }

    }

    @Test

    public void timeReadStatFileDirectly() throws Exception {

        final BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        // CPU usage by frequency for this pid. Data is in text format.

        final String procFile = "/proc/self/stat";

        while (state.keepRunning()) {

            byte[] data = Files.readAllBytes(Paths.get(procFile));

        }

    }

    @Test

    public void timeReadPidProcDirectly() throws Exception {

        final BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        // CPU usage by frequency for this pid. Data is in text format.

        final String procFile = "/proc/self/time_in_state";

        while (state.keepRunning()) {

            byte[] data = Files.readAllBytes(Paths.get(procFile));

        }

    }

    @Test

    public void timeReadThreadProcDirectly() throws Exception {

        final BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        // CPU usage by frequency for this UID. Data is in text format.

        final String procFile = "/proc/self/task/" + android.os.Process.myTid()

                + "/time_in_state";

        while (state.keepRunning()) {

            byte[] data = Files.readAllBytes(Paths.get(procFile));

        }

    }

}