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

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Date:	Mon, 28 Jan 2013 12:29:22 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Mike Galbraith <efault@....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, 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.

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?

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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