services/core/java/com/android/server/wm/WindowManagerThreadPriorityBooster.java

/*
 * Copyright (C) 2017 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 com.android.server.wm;

import static android.os.Process.THREAD_PRIORITY_DISPLAY;
import static android.os.Process.myTid;
import static android.os.Process.setThreadPriority;

import static com.android.server.LockGuard.INDEX_WINDOW;
import static com.android.server.am.ActivityManagerService.TOP_APP_PRIORITY_BOOST;

import com.android.server.AnimationThread;
import com.android.server.ThreadPriorityBooster;

/**
 * Window manager version of {@link ThreadPriorityBooster} that boosts even more during app
 * transitions.
 */
class WindowManagerThreadPriorityBooster extends ThreadPriorityBooster {

    private final AnimationThread mAnimationThread;
    private boolean mAppTransitionRunning;

    WindowManagerThreadPriorityBooster() {
        super(THREAD_PRIORITY_DISPLAY, INDEX_WINDOW);
        mAnimationThread = AnimationThread.get();
    }

    @Override
    public void boost() {

        // Do not boost the animation thread. As the animation thread is changing priorities,
        // boosting it might mess up the priority because we reset it the the previous priority.
        if (myTid() == mAnimationThread.getThreadId()) {
            return;
        }
        super.boost();
    }

    @Override
    public void reset() {

        // See comment in boost().
        if (myTid() == mAnimationThread.getThreadId()) {
            return;
        }
        super.reset();
    }

    void setAppTransitionRunning(boolean running) {
        if (mAppTransitionRunning == running) {
            return;
        }

        final int priority = calculatePriority(running);
        setBoostToPriority(priority);
        setThreadPriority(mAnimationThread.getThreadId(), priority);
        mAppTransitionRunning = running;
    }

    private int calculatePriority(boolean appTransitionRunning) {
        return appTransitionRunning ? TOP_APP_PRIORITY_BOOST : THREAD_PRIORITY_DISPLAY;
    }
}