多线程为多核处理器 [英] Multi-threading for multi-core processors
问题描述
我有三星Galaxy S3，它使用了自家的Exynos 4四核处理器。 所以，我要优化我的应用程序，它可以使用处理器的所有4个内核。
I have Samsung Galaxy S3, which used its own Exynos 4 Quad processor. So I want to optimize my app, that it can use all 4 cores of processor.
所以我做了一些测试：
-
在一个线程中运行任务。处理时间 - 8秒
Run task in one thread. Processing time - 8 seconds.
在四线程运行的任务。处理时间 - 还是8秒
Run task in four threads. Processing time - still 8 sec.
new Thread() {
public void run() {
// do 1/4 of task
}
}.start();
new Thread() {
public void run() {
// do 1/4 of task
}
}.start();
new Thread() {
public void run() {
// do 1/4 of task
}
}.start();
new Thread() {
public void run() {
// do 1/4 of task
}
}.start();
在ExecutorService的运行任务。和处理时间 - 还是8秒
Run task in ExecutorService. And processing time - still 8 sec.
ExecutorService threadPool = null;
threadPool = Executors.newFixedThreadPool(4);
threadPool.execute(new Runnable() {
@Override
public void run() {
// do 1/4 of task
}});
threadPool.execute(new Runnable() {
@Override
public void run() {
// do 1/4 of task
}});
threadPool.execute(new Runnable() {
@Override
public void run() {
// do 1/4 of task
}});
threadPool.execute(new Runnable() {
@Override
public void run() {
// do 1/4 of task
}});
看起来像同步完成所有的工作。为什么它不是并联？
Looks like all work done synchronously. Why its not paralleling ?
推荐答案
您可以尝试用C或Java我的测试中，
You can try my tests, in C or Java:
http://bigflake.com/cpu-spinner.c.txt < BR> http://bigflake.com/MultiCore.java.txt
http://bigflake.com/cpu-spinner.c.txt
http://bigflake.com/MultiCore.java.txt
当MultiCore.java运行在一台Nexus 4，我明白了：
When MultiCore.java is run on a Nexus 4, I see:
Thread 1 finished in 1516ms (1267234688)
Thread 3 finished in 1494ms (1519485328)
Thread 0 finished in 1530ms (51099776)
Thread 2 finished in 1543ms (-1106614992)
All threads finished in 1550ms
更新： 它是有用的观看测试与systrace。作为回答了类似的一部分<一href="http://stackoverflow.com/questions/17842864/multiprocessing-on-android/17959192#17959192">question我建立了一个网页，显示systrace输出此测试。你可以看到线程调度，并观看了另外两个内核旋转起来。
Update: It's useful to watch the test with systrace. As part of answering a similar question I set up a page that shows the systrace output for this test. You can see how the threads are scheduled, and watch the other two cores spin up.
这篇关于多线程为多核处理器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
