Question

我有一个使用Parallel::ForkManager的脚本。但是，即使在所有子进程完成之后，wait_all_children（）进程也需要非常长的时间。我知道的方法是打印一些时间戳（见下文）。有谁知道可能导致这种情况的原因（我的机器上有16个CPU内核）？

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，我会首先收到Waiting for some child process to finish消息，时间戳为7:08:35。然后，我将获得Process i completed条消息的列表，最后一条消息位于7:10:30。但是，在All Processes finished（！）之前，我才收到消息7:16:33。为什么在7:10:30到7:16:33之间有6分钟的延迟？ THX！

Answer 1

我试过了：

#!/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;

我得到了：

[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.

我在Parallel::ForkManager版本perl 5.10.1的Linux上0.7.5。

因此，我得出结论，无论您遇到什么问题，都是因为当您

时发生的事情

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

更新：问题是，您是在Process finished message来电之前打印finish。请尝试以下版本：

#!/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;

有关详细信息，请参阅Callbacks in Parallel::ForkManager documentation。如果延迟消失，那么您观察到的症状是由于您声称分叉过程在完成之前已完成。

Perl Parallel :: ForkManager wait_all_children（）花费的时间过长

1 个答案: