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

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Date:	Fri, 8 Aug 2014 07:15:35 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Jason Low <jason.low2@...com>, 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 Fri, Aug 08, 2014 at 09:11:03AM +0200, Peter Zijlstra wrote:
> On Fri, Aug 08, 2014 at 06:30:08AM +0800, Yuyang Du wrote:
> > > > > -----------------------------------------------------
> > > > >               |   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 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.
> 
> Been a bit busy.. but in general I worry about the performance decrease
> on the lighter loads. I should probably run some workloads on my 2
> socket and 4 socket machines, but the coming few weeks will be very busy
> and I'm afraid I'll not get around to it in a timely manner.

Ok. I understand. From our part, Fengguang's LKP does not include light loads,
we also need some such tests to confirm this and see what is next.

Since typical benchmarks would be heavy ones, what do you suggest for light loads?

Jason, possible you can share some of your workloads?

Thanks,
Yuyang
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