linux-kernel - Re: [patch v4 0/18] sched: simplified fork, release load avg and power awareness scheduling

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Message-ID: <1359372743.5783.136.camel@marge.simpson.net>
Date:	Mon, 28 Jan 2013 12:32:23 +0100
From:	Mike Galbraith <efault@....de>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Alex Shi <alex.shi@...el.com>, torvalds@...ux-foundation.org,
	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, pjt@...gle.com,
	namhyung@...nel.org, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 0/18] sched: simplified fork, release load avg and
 power awareness scheduling

On Mon, 2013-01-28 at 12:29 +0100, Borislav Petkov wrote: 
> On Mon, Jan 28, 2013 at 11:44:44AM +0100, Mike Galbraith wrote:
> > On Mon, 2013-01-28 at 10:55 +0100, Borislav Petkov wrote: 
> > > On Mon, Jan 28, 2013 at 06:17:46AM +0100, Mike Galbraith wrote:
> > > > Zzzt.  Wish I could turn turbo thingy off.
> > > 
> > > Try setting /sys/devices/system/cpu/cpufreq/boost to 0.
> > 
> > How convenient (test) works too.
> > 
> > So much for turbo boost theory.  Nothing changed until I turned load
> > balancing off at NODE.  High end went to hell (gee), but low end... 
> >   
> > Benchmark       Version Machine Run Date
> > AIM Multiuser Benchmark - Suite VII     "1.1"   performance-no-node-load_balance Jan 28 11:20:12 2013
> > 
> > Tasks   Jobs/Min        JTI     Real    CPU     Jobs/sec/task
> > 1       436.3           100     13.9    3.9     7.2714
> > 5       2637.1          99      11.5    7.3     8.7903
> > 10      5415.5          99      11.2    11.3    9.0259
> > 20      10603.7         99      11.4    24.8    8.8364
> > 40      20066.2         99      12.1    40.5    8.3609
> > 80      35079.6         99      13.8    75.5    7.3082
> > 160     55884.7         98      17.3    145.6   5.8213
> > 320     79345.3         98      24.4    287.4   4.1326
> 
> If you're talking about those results from earlier:
> 
> Benchmark       Version Machine Run Date
> AIM Multiuser Benchmark - Suite VII     "1.1"   performance     Jan 28 08:09:20 2013
> 
> Tasks   Jobs/Min        JTI     Real    CPU     Jobs/sec/task
> 1       438.8           100     13.8    3.8     7.3135
> 5       2634.8          99      11.5    7.2     8.7826
> 10      5396.3          99      11.2    11.4    8.9938
> 20      10725.7         99      11.3    24.0    8.9381
> 40      20183.2         99      12.0    38.5    8.4097
> 80      35620.9         99      13.6    71.4    7.4210
> 160     57203.5         98      16.9    137.8   5.9587
> 320     81995.8         98      23.7    271.3   4.2706
> 
> then the above no_node-load_balance thing suffers a small-ish dip at 320
> tasks, yeah.

No no, that's not restricted to one node.  It's just overloaded because
I turned balancing off at the NODE domain level.

> And AFAICR, the effect of disabling boosting will be visible in the
> small count tasks cases anyway because if you saturate the cores with
> tasks, the boosting algorithms tend to get the box out of boosting for
> the simple reason that the power/perf headroom simply disappears due to
> the SOC being busy.
> 
> > 640     100294.8        98      38.7    570.9   2.6118
> > 1280    115998.2        97      66.9    1132.8  1.5104
> > 2560    125820.0        97      123.3   2256.6  0.8191
> 
> I dunno about those. maybe this is expected with so many tasks or do we
> want to optimize that case further?

When using all 4 nodes properly, that's still scaling.  Here, I
intentionally screwed up balancing to watch the low end.  High end is
expected wreckage.

-Mike


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