android_frameworks_base/tools/preload/WritePreloadedClassFile.java

/*
 * Copyright (C) 2008 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.
 */

import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.util.Set;
import java.util.TreeSet;

/**
 * Writes /frameworks/base/preloaded-classes. Also updates LoadedClass.preloaded
 * fields and writes over compiled log file.
 */
public class WritePreloadedClassFile {

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        if (args.length != 1) {
            System.err.println("Usage: WritePreloadedClassFile [compiled log]");
            System.exit(-1);
        }
        String rootFile = args[0];
        Root root = Root.fromFile(rootFile);

        // No classes are preloaded to start.
        for (LoadedClass loadedClass : root.loadedClasses.values()) {
            loadedClass.preloaded = false;
        }

        // Open preloaded-classes file for output.
        Writer out = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(Policy.getPreloadedClassFileName()),
                Charset.forName("US-ASCII")));

        out.write("# Classes which are preloaded by com.android.internal.os.ZygoteInit.\n");
        out.write("# Automatically generated by /frameworks/base/tools/preload.\n");
        out.write("# percent=" + Proc.PERCENTAGE_TO_PRELOAD
                + ", weight=" + ClassRank.SEQUENCE_WEIGHT
                + ", bucket_size=" + ClassRank.BUCKET_SIZE
                + "\n");

        Set<LoadedClass> toPreload = new TreeSet<LoadedClass>();

        // Preload all classes that were loaded by at least 2 apps, if both
        // apps run at the same time, they'll share memory.
        for (LoadedClass loadedClass : root.loadedClasses.values()) {
            if (!loadedClass.isPreloadable()) {
                continue;
            }

            Set<String> appNames = loadedClass.applicationNames();

            if (appNames.size() > 3) {
                toPreload.add(loadedClass);
            }
        }

        // Try to make individual apps start faster by preloading slowest
        // classes.
        for (Proc proc : root.processes.values()) {
            toPreload.addAll(proc.highestRankedClasses());
        }

        System.out.println(toPreload.size() + " classes will be preloaded.");

        // Make classes that were already loaded by the zygote explicit.
        // This adds minimal overhead but avoid confusion about classes not
        // appearing in the list.
        addAllClassesFor("zygote", root, toPreload);

        for (LoadedClass loadedClass : toPreload) {
            out.write(loadedClass.name);
            out.write('\n');
        }

        out.close();

        // Update data to reflect LoadedClass.preloaded changes.
        for (LoadedClass loadedClass : toPreload) {
            loadedClass.preloaded = true;
        }
        root.toFile(rootFile);
    }

    private static void addAllClassesFor(String packageName, Root root,
                                         Set<LoadedClass> toPreload) {
        for (Proc proc : root.processes.values()) {
            if (proc.name.equals(packageName)) {
                for (Operation operation : proc.operations) {
                    // TODO: I'm not sure how the zygote loaded classes that
                    // aren't supposed to be preloadable...
                    if (operation.loadedClass.isPreloadable()) {
                        toPreload.add(operation.loadedClass);
                    }
                }
            }
        }
    }
}