Perl的并行:: ForkManager wait_all_children（）采用过长的时间

Question

我有一个使用Parallel::ForkManager的脚本。然而，wait_all_children（）过程需要所有的子流程完成后，甚至令人难以置信的很长一段时间。我知道的方法是打印出一些时间戳（见下文）。没有人有任何想法可能是造成这个（我有我的机器上16个CPU核心）？

my $pm = Parallel::ForkManager->new(16);
for my $i (1..16) {
    $pm->start($i) and next;

    ... do something within the child-process ...

    print (scalar localtime), " Process $i completed.\n";
    $pm->finish();
}
print (scalar localtime), " Waiting for some child process to finish.\n"; 
$pm->wait_all_children();
print (scalar localtime), " All processes finished.\n"; 

显然，我会先拿到Waiting for some child process to finish消息，有，比方说，7:08:35时间戳。然后，我会得到Process i completed的邮件列表，与7:10:30最后一个。不过，我没有收到消息All Processes finished直到7:16:33（！）。这是为什么七时10分三十○秒和7时16分33秒之间的6分钟的延迟？ THX！

Answer 1

我尝试这样：

#!/opt/perl/bin/perl

use strict; use warnings;

use Parallel::ForkManager;

my $pm = Parallel::ForkManager->new(16);

for my $i (1..16) {
    $pm->start($i) and next;
    sleep rand 20;
    printf "%s : Process %d completed\n", scalar localtime, $i;
    $pm->finish;
}

printf "%s: Waiting for some child to finish\n", scalar localtime;
$pm->wait_all_children;

printf "%s: All processes finished.\n", scalar localtime; 

我得到：

[sinan@archardy Src]$ ./y.pl
Thu Mar 11 17:14:16 2010 : Process 3 completed
Thu Mar 11 17:14:16 2010: Waiting for some child to finish
Thu Mar 11 17:14:18 2010 : Process 8 completed
Thu Mar 11 17:14:18 2010 : Process 14 completed
<snip>...</snip>
Thu Mar 11 17:14:34 2010 : Process 12 completed
Thu Mar 11 17:14:34 2010: All processes finished.

我perl 5.10.1的Linux上并行:: ForkManager 的版本0.7.5。

因此，我的结论是无论您有正在发生的会发生什么后果问题，当您

# ... do something within the child-process ...

更新：的问题是，要打印的Process finished message调用之前finish。尝试下面的版本：

#!/opt/perl/bin/perl

use strict; use warnings;

use Parallel::ForkManager;

my $pm = Parallel::ForkManager->new(16);
$pm->run_on_finish( sub {
    printf "%s : Process completed: @_\n", scalar localtime
});

for my $i (1..16) {
    $pm->start($i) and next;
    sleep rand 20;
    $pm->finish;
}

printf "%s: Waiting for some child to finish\n", scalar localtime;
$pm->wait_all_children;

printf "%s: All processes finished.\n", scalar localtime;

有关的更多信息请参见回调并行:: ForkManager文档。如果延迟消失，那么你所观察的症状是由于这样的事实，你是自称派生进程已经完成了它之前完成。