linux-kernel - Re: [GIT TREE] Unified NUMA balancing tree, v3

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Message-ID: <20121210200755.GA15097@gmail.com>
Date:	Mon, 10 Dec 2012 21:07:55 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Rik van Riel <riel@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [GIT TREE] Unified NUMA balancing tree, v3


* Mel Gorman <mgorman@...e.de> wrote:

> On Mon, Dec 10, 2012 at 08:15:45PM +0100, Ingo Molnar wrote:
> > 
> > * Rik van Riel <riel@...hat.com> wrote:
> > 
> > > On 12/10/2012 01:22 PM, Thomas Gleixner wrote:
> > > 
> > > > So autonuma and numacore are basically on the same page, 
> > > > with a slight advantage for numacore in the THP enabled 
> > > > case. balancenuma is closer to mainline than to 
> > > > autonuma/numacore.
> > > 
> > > Indeed, when the system is fully loaded, numacore does very 
> > > well.
> > 
> > Note that the latest (-v3) code also does well in under-loaded 
> > situations:
> > 
> >    http://lkml.org/lkml/2012/12/7/331
> > 
> > Here's the 'perf bench numa' comparison to 'balancenuma':
> > 
> >                             balancenuma  | NUMA-tip
> >  [test unit]            :          -v10  |    -v3
> > ------------------------------------------------------------
> >  2x1-bw-process         :         6.136  |  9.647:  57.2%
> >  3x1-bw-process         :         7.250  | 14.528: 100.4%
> >  4x1-bw-process         :         6.867  | 18.903: 175.3%
> >  8x1-bw-process         :         7.974  | 26.829: 236.5%
> >  8x1-bw-process-NOTHP   :         5.937  | 22.237: 274.5%
> >  16x1-bw-process        :         5.592  | 29.294: 423.9%
> >  4x1-bw-thread          :        13.598  | 19.290:  41.9%
> >  8x1-bw-thread          :        16.356  | 26.391:  61.4%
> >  16x1-bw-thread         :        24.608  | 29.557:  20.1%
> >  32x1-bw-thread         :        25.477  | 30.232:  18.7%
> >  2x3-bw-thread          :         8.785  | 15.327:  74.5%
> >  4x4-bw-thread          :         6.366  | 27.957: 339.2%
> >  4x6-bw-thread          :         6.287  | 27.877: 343.4%
> >  4x8-bw-thread          :         5.860  | 28.439: 385.3%
> >  4x8-bw-thread-NOTHP    :         6.167  | 25.067: 306.5%
> >  3x3-bw-thread          :         8.235  | 21.560: 161.8%
> >  5x5-bw-thread          :         5.762  | 26.081: 352.6%
> >  2x16-bw-thread         :         5.920  | 23.269: 293.1%
> >  1x32-bw-thread         :         5.828  | 18.985: 225.8%
> >  numa02-bw              :        29.054  | 31.431:   8.2%
> >  numa02-bw-NOTHP        :        27.064  | 29.104:   7.5%
> >  numa01-bw-thread	:        20.338  | 28.607:  40.7%
> >  numa01-bw-thread-NOTHP :        18.528  | 21.119:  14.0%
> > ------------------------------------------------------------
> > 
> > More than half of these testcases are under-loaded situations.
> > 
> > > The main issues that have been observed with numacore are when 
> > > the system is only partially loaded. Something strange seems 
> > > to be going on that causes performance regressions in that 
> > > situation.
> > 
> > I haven't seen such reports with -v3 yet, which is what Thomas 
> > tested. Mel has not tested -v3 yet AFAICS.
> > 
> 
> Yes, I have. The drop I took and the results I posted to you 
> were based on a tip/master pull from December 9th. v3 was 
> released on December 7th and your release said to test based 
> on tip/master. The results are here 
> https://lkml.org/lkml/2012/12/9/108 . Look at the columns 
> marked numafix-20121209 which is tip/master with a bodge on 
> top to remove the "if (p->nr_cpus_allowed != 
> num_online_cpus())" check.

Ah, indeed - I saw those results but the 'numafix' tag threw me 
off.

Looks like at least in terms of AutoNUMA-benchmark numbers you 
measured the best-ever results with the -v3 tree? That aspect is 
obviously good news.

This part isn't:

> > If there are any such instances left then I'll investigate, 
> > but right now it's looking pretty good.
> 
> If you had read that report, you would know that I didn't have 
> results for specjbb with THP enabled due to the JVM crashing 
> with null pointer exceptions.

Hm, it's the unified tree where most of the mm/ bits are the 
AutoNUMA bits from your tree. (It does not match 100%, because 
your tree has an ancient version of key memory usage statistics 
that the scheduler needs for its convergence model. I'll take a 
look at the differences.)

Given how well the unified kernel performs, and given that the 
segfaults occur on your box, would you be willing to debug this 
a bit and help me out fixing the bug? Thanks!

	Ingo
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