NSOperationQueue不重用iPhone上的线程 [英] NSOperationQueue not reusing thread on iPhone

问题描述

我使用的是iPhone SDK 3.1.2，以下代码显示NSOperationQueue不会为每个任务重复使用该线程。

I'm using iPhone SDK 3.1.2, and the following code shows the NSOperationQueue does not reuse the thread for each task.

代码没有任何雪豹的问题。

The code does not have any problems on Snow Leopard.

- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after app launch    
    [window addSubview:viewController.view];
    [window makeKeyAndVisible];

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    [queue setMaxConcurrentOperationCount:1];
    for(int i = 0; i < 100; i++) {
        NSInvocationOperation *op = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(run) object:nil];
        [queue addOperation:op];
        [op release];
    }
}

- (void)run {
    static int tc = 0;
    if([[NSThread currentThread] isMainThread]) {
        NSLog(@"MAIN THREAD");
        return;
    } else if([[NSThread currentThread] name] == nil) {
        [[NSThread currentThread] setName:[NSString stringWithFormat:@"THREAD_%d", tc++]];
    }
    NSLog(@"%@", [[NSThread currentThread] name]);
}

输出显示它创建100个线程来执行100个任务。

The output shows it create 100 threads to execute the 100 tasks.

2010-01-07 11:46:03.502 OperationQueueTest[7911:4503] THREAD_0
2010-01-07 11:46:03.506 OperationQueueTest[7911:4d03] THREAD_1
2010-01-07 11:46:03.507 OperationQueueTest[7911:4807] THREAD_2
2010-01-07 11:46:03.510 OperationQueueTest[7911:4d07] THREAD_3
2010-01-07 11:46:03.514 OperationQueueTest[7911:5007] THREAD_4
2010-01-07 11:46:03.516 OperationQueueTest[7911:4f0b] THREAD_5
2010-01-07 11:46:03.518 OperationQueueTest[7911:4e0f] THREAD_6
...
2010-01-07 11:46:03.740 OperationQueueTest[7911:4ea7] THREAD_97
2010-01-07 11:46:03.744 OperationQueueTest[7911:4dcf] THREAD_98
2010-01-07 11:46:03.746 OperationQueueTest[7911:460f] THREAD_99

推荐答案

NSOperationQueue设计用于以最有效的方式池和重用线程，在这种情况下，似乎决定不重新 - 使用线程是最好的方法。

NSOperationQueue is designed to pool and re-use threads in the most efficient way possible and in this instance, it seems it decided not re-using threads was the best way to go.

测试代码有它的用途（和你可能已经确定了一个角落的情况下，NSOperationQueue不能做到最有效率事情），但这并不意味着NSOperationQueue在处理真实代码在现实生活中总是可怕的低效;实际上我自己的经验是相反的。

Test code has it's uses (and it is possible you may have identified a corner case where NSOperationQueue does not do the most efficient thing), but that doesn't mean that NSOperationQueue is always horribly inefficient when dealing with real code in real life; in fact my own experience has been to the contrary.

所以我想说在你的实际代码中使用它，如果你有性能问题，进一步挖掘它做什么与幕后的线程。

So I'd say use it in your real code and if you have performance issues, dig further into what it's doing with threads behind the scenes. Otherwise don't worry about it.

另外，如果你仍然好奇，你可以尝试将线程的名称记录到一个NSStrings数组，然后打印一切都在测试代码的结尾，而不是记录，因为这将显着减少每个NSInvocationOperation所做的工作量。

As an aside, if you are still curious, you might try recording the names of the threads into an array of NSStrings and then printing everything out at the end of the test code, rather than logging as you go along - this will significantly reduce the amount of work done by each NSInvocationOperation.

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