linux-kernel - Re: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)

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Date:	Wed, 08 Aug 2007 16:38:59 +0200
From:	Kasper Sandberg <lkml@...anurb.dk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ck@....kolivas.org
Subject: Re: SD still better than CFS for 3d   ?(was Re: 2.6.23-rc1)

First off, sorry for the late response.

On Thu, 2007-08-02 at 17:42 +0200, Ingo Molnar wrote: 
> Kasper,
> 
> could you please try the "chew-max" latency-printing utility:
> 
>    http://people.redhat.com/mingo/cfs-scheduler/tools/chew-max.c
> 
> if you start it on an idle system it prints a single line:
> 
>   $ ./chew-max
>   pid 14506, prio   0, interval of 99984800 nsec
> 
> and prints nothing else. It continues looping and looping (using up 100% 
> of CPU time), and the moment it's preempted, it prints a line about that 
> preemption latency. Under higher load it will print something like this:
> 
>   out for   63 ms [max:   66], ran for    5 ms, load   7
>   out for   85 ms [max:   85], ran for    4 ms, load   5
>   out for    7 ms [max:   85], ran for    0 ms, load   0
>   out for  105 ms [max:  105], ran for    3 ms, load   3
>   out for  174 ms [max:  174], ran for    6 ms, load   3
>   out for  219 ms [max:  219], ran for    3 ms, load   1
>   out for   78 ms [max:  219], ran for    3 ms, load   3
> 
> so that we get a picture of your latencies, could you run this tool why 
> you are seeing those 'bad' desktop latencies? (Since your CPU has two 
bad is not the exact word, its pretty good, certainly better than old
vanilla scheduler, just not as smooth as could be. 
> cores it might make sense to run two instances of chew-max.)

its a singlecore socket 754 firstgen amd64 :)

> 
> record the latencies like this:
> 
>   ./chew-max > chew1.out &
>   ./chew-max > chew2.out &
> 
> and send us the chew1.out and chew2.out files (bzip2 -9 compressed). 
> Thanks!

i've attached it(bzip2'ed)

i've come to think it is IO related, but not entirely related to
reiserfs, perhaps xfs.

i will conduct some tests as soon as possible.

> 
> 	Ingo
> -
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View attachment "chewout.log" of type "text/x-log" (12327 bytes)