Re: fork() 50 times slower on some Linux kernels?

From	Nobody <nobody@nowhere.com>
Subject	Re: fork() 50 times slower on some Linux kernels?
Date	2012-01-10 23:07 +0000
Message-Id	<pan.2012.01.10.23.07.00.764000@nowhere.com>
Newsgroups	comp.lang.c
References	<20147768-1b78-4ac5-84e5-607c1d47c6a6@dp8g2000vbb.googlegroups.com> <jefong$a4q$1@dont-email.me> <20120109140729.280@kylheku.com> <jefso9$8mo$1@dont-email.me>
Organization	Zen Internet

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On Mon, 09 Jan 2012 17:20:40 -0600, Stephen Sprunk wrote:

> Disabling overcommitment moves that problem to the present by forcing
> the kernel to find backing for all those pages during the fork(), and
> that takes time.

Why would it take time? Obviously it takes _some_ time, but there's no
need for it to take significant time. It only has to check that the number
of shared (copy-on-write) pages is less than the number of uncommitted
pages, then subtract the former from the latter. It doesn't have to
actually do anything with those pages.

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fork() 50 times slower on some Linux kernels? Elmar <elmar.krieger@gmail.com> - 2012-01-09 12:25 -0800
  Re: fork() 50 times slower on some Linux kernels? Ian Collins <ian-news@hotmail.com> - 2012-01-10 09:41 +1300
  Re: fork() 50 times slower on some Linux kernels? Kaz Kylheku <kaz@kylheku.com> - 2012-01-09 21:32 +0000
    [OT] Re: fork() 50 times slower on some Linux kernels? jt@toerring.de (Jens Thoms Toerring) - 2012-01-09 22:12 +0000
      Re: [OT] Re: fork() 50 times slower on some Linux kernels? Kaz Kylheku <kaz@kylheku.com> - 2012-01-09 22:32 +0000
        Re: [OT] Re: fork() 50 times slower on some Linux kernels? Ian Collins <ian-news@hotmail.com> - 2012-01-10 11:56 +1300
  Re: fork() 50 times slower on some Linux kernels? Stephen Sprunk <stephen@sprunk.org> - 2012-01-09 16:11 -0600
    Re: fork() 50 times slower on some Linux kernels? Kaz Kylheku <kaz@kylheku.com> - 2012-01-09 22:30 +0000
      Re: fork() 50 times slower on some Linux kernels? Stephen Sprunk <stephen@sprunk.org> - 2012-01-09 17:20 -0600
        Re: [OT] fork() 50 times slower on some Linux kernels? jt@toerring.de (Jens Thoms Toerring) - 2012-01-09 23:57 +0000
          Re: [OT] fork() 50 times slower on some Linux kernels? Kaz Kylheku <kaz@kylheku.com> - 2012-01-10 00:22 +0000
            Re: [OT] fork() 50 times slower on some Linux kernels? Stephen Sprunk <stephen@sprunk.org> - 2012-01-09 20:39 -0600
              Re: [OT] fork() 50 times slower on some Linux kernels? William Ahern <william@wilbur.25thandClement.com> - 2012-01-09 19:43 -0800
                Re: [OT] fork() 50 times slower on some Linux kernels? Stephen Sprunk <stephen@sprunk.org> - 2012-01-10 00:31 -0600
          Re: fork() 50 times slower on some Linux kernels? Elmar <elmar.krieger@gmail.com> - 2012-01-11 14:39 -0800
        Re: fork() 50 times slower on some Linux kernels? Nobody <nobody@nowhere.com> - 2012-01-10 23:07 +0000

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