cat /proc/net/tcp takes 0.5 seconds on x86_64

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From: Dave Jones
Date: Tuesday, August 26, 2008 - 9:37 am

Just had this bug reported against our development tree..

	Dave

On Tue, Aug 26, 2008 at 11:49:31AM -0400, bugzilla@redhat.com wrote:
 > Please do not reply directly to this email. All additional
 > comments should be made in the comments box of this bug.
 > 
 > https://bugzilla.redhat.com/show_bug.cgi?id=459782
 > 
 > Hans de Goede <j.w.r.degoede@hhs.nl> changed:
 > 
 >            What    |Removed                     |Added
 > ----------------------------------------------------------------------------
 >                  CC|                            |j.w.r.degoede@hhs.nl
 >           Component|gkrellm                     |kernel
 >          AssignedTo|j.w.r.degoede@hhs.nl        |kernel-maint@redhat.com
 >             Summary|gkrellmd consumes about 75% |cat /proc/net/tcp takes 0.5
 >                    |cpu time                    |seconds on x86_64, 0.5
 >                    |                            |seconds !!
 > 
 > --- Comment #2 from Hans de Goede <j.w.r.degoede@hhs.nl>  2008-08-26 11:49:30 EDT ---
 > Thanks for reporting this some stracing of gkrellmd has found that reading from
 > /proc/net/tcp and reading from /proc/net/tcp6 is the culprit, try this on your
 > x86_64 machine to confirm:
 > 
 > "time cat /proc/net/tcp"
 > 
 > To give you an idea on my rawhide x86_64 machine:
 > [hans@localhost devel]$ time cat /proc/net/tcp
 > <snip>
 > real    0m0.520s
 > user    0m0.000s
 > sys     0m0.446s
 > 
 > Thats amazingly slow, esp as I only have 8 tcp connections open.
 > 
 > Some maybe usefull info: top reports a very high load (50%) from soft IRQ's.
 > 
 > Anyways changing this to a kernel bug.

-- 
http://www.codemonkey.org.uk
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Messages in current thread:
cat /proc/net/tcp takes 0.5 seconds on x86_64, Dave Jones, (Tue Aug 26, 9:37 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Tue Aug 26, 11:32 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Hans de Goede, (Tue Aug 26, 12:01 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Tue Aug 26, 1:39 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Hans de Goede, (Tue Aug 26, 1:58 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Tue Aug 26, 2:27 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Herbert Xu, (Tue Aug 26, 9:19 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 2:05 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Hans de Goede, (Wed Aug 27, 2:07 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Hans de Goede, (Wed Aug 27, 2:14 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 2:39 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Hans de Goede, (Wed Aug 27, 2:45 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 5:41 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Trent Piepho, (Wed Aug 27, 2:29 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 2:29 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 2:47 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Stephen Hemminger, (Wed Aug 27, 2:48 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 3:09 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 3:34 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 3:39 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 3:54 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 3:57 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 4:07 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Wed Aug 27, 4:09 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 4:15 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Wed Aug 27, 4:35 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Wed Aug 27, 4:43 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 4:45 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Wed Aug 27, 5:40 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Wed Aug 27, 11:20 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Wed Aug 27, 11:51 pm)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Eric Dumazet, (Thu Aug 28, 12:13 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Thu Aug 28, 12:26 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, Andi Kleen, (Thu Aug 28, 12:45 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Thu Aug 28, 12:57 am)
Re: cat /proc/net/tcp takes 0.5 seconds on x86_64, David Miller, (Thu Aug 28, 12:59 am)