popen管减慢其他线程 [英] popen pipe slows down other threads

问题描述

我的多线程应用程序有问题。当在一个线程执行同步 popen（）命令 - 其他应用程序线程显着减慢。用 popen（）的线程执行 ffmpeg ，会产生高负载。

$ b b

通常，其他线程的执行时间为0.0007 ms。当使用 popen 时，某些线程的执行时间增加到14-20秒。

如何解决这个问题？

系统是FreeBSD 6.4

  FILE * pipe; 
 char buff [512]; 
 if（！（pipe = popen（command.c_str（），r）））
 {//如果pipe为NULL 
 return false; 
} 
 
 while（fgets（buff，sizeof（buff），pipe）！= NULL）
 {
 ptr_output-& 
} 
  

这里是popen的新代码，不会帮助：正确的代码 - 带有popen的非阻塞管道

< fgets是一个阻塞读取，所以当上面的线程正在等待从管道读取数据时，其他线程被阻塞。您将希望对文件描述符使用select / poll，以查看在发出读取之前是否在管道上有数据。这样，你可以抢占这个线程，并让其他线程运行做有用的工作。

I have problem with my multithread application. When at one thread executing synchronous popen() command - other application threads are slow down significantly. Thread with popen() execute ffmpeg, that generates high load.

Normally, other threads execution time is 0.0007 ms. And when popen is used, some threads are increasing there execution time up to 14-20 seconds.

How to solve this problem?

System is FreeBSD 6.4

    FILE *pipe;
    char buff[512];
    if ( !(pipe = popen( command.c_str(), "r")) )
    { // if pipe is NULL
        return false;
    }

    while ( fgets(buff, sizeof(buff), pipe) != NULL )
    {
        ptr_output->append(buff);
    }

here is new code of popen can that does NOT help: Correct Code - Non-blocking pipe with popen

解决方案

fgets is a blocking read, so while the thread above is waiting for data to be read from the pipe, the other threads are blocked. You will want to use select/poll for with a file descriptor to see if you have data on the pipe before you issue a read. That way, you can preempt this thread, and let other threads run doing useful work.

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