linux-kernel - Re: [RFC PATCH 0/2] sched: simplify the select_task_rq

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Date:	Mon, 21 Jan 2013 10:11:16 +0100
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com,
	peterz@...radead.org, mingo@...nel.org, a.p.zijlstra@...llo.nl
Subject: Re: [RFC PATCH 0/2] sched: simplify the select_task_rq_fair()

On Mon, 2013-01-21 at 16:46 +0800, Michael Wang wrote: 
> On 01/21/2013 04:26 PM, Mike Galbraith wrote:
> > On Mon, 2013-01-21 at 15:34 +0800, Michael Wang wrote: 
> >> On 01/21/2013 02:42 PM, Mike Galbraith wrote:
> >>> On Mon, 2013-01-21 at 13:07 +0800, Michael Wang wrote:
> >>>
> >>>> That seems like the default one, could you please show me the numbers in
> >>>> your datapoint file?
> >>>
> >>> Yup, I do not touch the workfile.  Datapoints is what you see in the
> >>> tabulated result...
> >>>
> >>> 1
> >>> 1
> >>> 1
> >>> 5
> >>> 5
> >>> 5
> >>> 10
> >>> 10
> >>> 10
> >>> ...
> >>>
> >>> so it does three consecutive runs at each load level.  I quiesce the
> >>> box, set governor to performance, echo 250 32000 32 4096
> >>>> /proc/sys/kernel/sem, then ./multitask -nl -f, and point it
> >>> at ./datapoints.
> >>
> >> I have changed the "/proc/sys/kernel/sem" to:
> >>
> >> 2000    2048000 256     1024
> >>
> >> and run few rounds, seems like I can't reproduce this issue on my 12 cpu
> >> X86 server:
> >>
> >> 	prev		post
> >> Tasks    jobs/min  	jobs/min
> >>     1      508.39    	506.69
> >>     5     2792.63   	2792.63
> >>    10     5454.55   	5449.64
> >>    20    10262.49  	10271.19
> >>    40    18089.55  	18184.55
> >>    80    28995.22  	28960.57
> >>   160    41365.19  	41613.73
> >>   320    53099.67  	52767.35
> >>   640    61308.88  	61483.83
> >>  1280    66707.95  	66484.96
> >>  2560    69736.58  	69350.02
> >>
> >> Almost nothing changed...I would like to find another machine and do the
> >> test again later.
> > 
> > Hm.  Those numbers look odd.  Ok, I've got 8 more cores, but your hefty
> > load throughput is low.  When I look low end numbers, seems your cores
> > are more macho than my 2.27 GHz EX cores, so it should have been a lot
> > closer.  Oh wait, you said "12 cpu".. so 1 6 core package + HT?  This
> > box is 2 NUMA nodes (was 4), 2 (was 4) 10 core packages + HT.
> 
> It's a 12 core package, and only 1 physical cpu:
> 
> Intel(R) Xeon(R) CPU           X5690  @ 3.47GHz
> 
> So does that means the issue was related to the case when there are
> multiple nodes?

Seems likely.  I had 4 nodes earlier though, and did NOT see collapse.

-Mike

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