linux-kernel - Re: [PATCH] sched: Reduce contention in update_cfs_rq_blocked

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Date:	Fri, 8 Aug 2014 06:30:08 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Jason Low <jason.low2@...com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Ben Segall <bsegall@...gle.com>,
	Waiman Long <Waiman.Long@...com>, Mel Gorman <mgorman@...e.de>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Aswin Chandramouleeswaran <aswin@...com>
Subject: Re: [PATCH] sched: Reduce contention in update_cfs_rq_blocked_load

On Thu, Aug 07, 2014 at 09:18:52PM -0700, Jason Low wrote:
> On Fri, 2014-08-08 at 02:02 +0800, Yuyang Du wrote:
> > On Wed, Aug 06, 2014 at 11:21:35AM -0700, Jason Low wrote:
> > > I ran these tests with most of the AIM7 workloads to compare its
> > > performance between a 3.16 kernel and the kernel with these patches
> > > applied.
> > > 
> > > The table below contains the percent difference between the baseline
> > > kernel and the kernel with the patches at various user counts. A
> > > positive percent means the kernel with the patches performed better,
> > > while a negative percent means the baseline performed better.
> > > 
> > > Based on these numbers, for many of the workloads, the change was
> > > beneficial in those highly contended, while it had - impact in many
> > > of the lightly/moderately contended case (10 to 90 users).
> > > 
> > > -----------------------------------------------------
> > >               |   10-90   |  100-1000   |  1100-2000
> > >               |   users   |   users     |   users
> > > -----------------------------------------------------
> > > alltests      |   -3.37%  |  -10.64%    |   -2.25%
> > > -----------------------------------------------------
> > > all_utime     |   +0.33%  |   +3.73%    |   +3.33%
> > > -----------------------------------------------------
> > > compute       |   -5.97%  |   +2.34%    |   +3.22%
> > > -----------------------------------------------------
> > > custom        |  -31.61%  |  -10.29%    |  +15.23%
> > > -----------------------------------------------------
> > > disk          |  +24.64%  |  +28.96%    |  +21.28%
> > > -----------------------------------------------------
> > > fserver       |   -1.35%  |   +4.82%    |   +9.35%
> > > -----------------------------------------------------
> > > high_systime  |   -6.73%  |   -6.28%    |  +12.36%
> > > -----------------------------------------------------
> > > shared        |  -28.31%  |  -19.99%    |   -7.10%
> > > -----------------------------------------------------
> > > short         |  -44.63%  |  -37.48%    |  -33.62%
> > > -----------------------------------------------------
> > > 
> > Thanks, Jason. Sorry for late response.
> > 
> > What about the variation of the tests? The machine you test on?
> 
> Hi Yuyang,
> 
> These tests were also done on an 8 socket machine (80 cores). In terms
> of variation between the average throughputs, typically the noise range
> is about 2% in many of the workloads.
> 

Thanks a lot, Jason.

So for this particular set of workloads on a big machine, I think the
result is mixed and overall "neutral", but I expected the variation probably
could be bigger especially for light workloads.

Any comment from the maintainers and others? Ping Peter and Ben, I haven't
heard from you for the 5th version.

Yuyang
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