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From: Ingo Molnar <mingo@kernel.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Mel Gorman <mgorman@techsingularity.net>,
	Rik van Riel <riel@surriel.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 2/6] mm/migrate: Use trylock while resetting rate limit
Date: Mon, 10 Sep 2018 10:39:25 +0200	[thread overview]
Message-ID: <20180910083925.GB48257@gmail.com> (raw)
In-Reply-To: <1533276841-16341-3-git-send-email-srikar@linux.vnet.ibm.com>


* Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:

> Since this spinlock will only serialize migrate rate limiting,
> convert the spinlock to a trylock. If another task races ahead of this task
> then this task can simply move on.
> 
> While here, add correct two abnormalities.
> - Avoid time being stretched for every interval.
> - Use READ/WRITE_ONCE with next window.
> 
> specjbb2005 / bops/JVM / higher bops are better
> on 2 Socket/2 Node Intel
> JVMS  Prev    Current  %Change
> 4     206350  200892   -2.64502
> 1     319963  325766   1.81365
> 
> 
> on 2 Socket/2 Node Power9 (PowerNV)
> JVMS  Prev    Current  %Change
> 4     186539  190261   1.99529
> 1     220344  195305   -11.3636
> 
> 
> on 4 Socket/4 Node Power7
> JVMS  Prev    Current  %Change
> 8     56836   57651.1  1.43413
> 1     112970  111351   -1.43312
> 
> 
> dbench / transactions / higher numbers are better
> on 2 Socket/2 Node Intel
> count  Min      Max      Avg      Variance  %Change
> 5      13136.1  13170.2  13150.2  14.7482
> 5      12254.7  12331.9  12297.8  28.1846   -6.48203
> 
> 
> on 2 Socket/4 Node Power8 (PowerNV)
> count  Min      Max      Avg      Variance  %Change
> 5      4319.79  4998.19  4836.53  261.109
> 5      4997.83  5030.14  5015.54  12.947    3.70121
> 
> 
> on 2 Socket/2 Node Power9 (PowerNV)
> count  Min      Max      Avg      Variance  %Change
> 5      9325.56  9402.7   9362.49  25.9638
> 5      9331.84  9375.11  9352.04  16.0703   -0.111616
> 
> 
> on 4 Socket/4 Node Power7
> count  Min      Max      Avg      Variance  %Change
> 5      132.581  191.072  170.554  21.6444
> 5      147.55   181.605  168.963  11.3513   -0.932842

Firstly, *please* always characterize benchmark runs. What did you find? How should we 
interpret the result? Are there any tradeoffs?

*Don't* just dump them on us.

Because in this particular case the results are not obvious, at all:

> specjbb2005 / bops/JVM / higher bops are better
> on 2 Socket/2 Node Intel
> JVMS  Prev    Current  %Change
> 4     206350  200892   -2.64502
> 1     319963  325766   1.81365
> 
> 
> on 2 Socket/2 Node Power9 (PowerNV)
> JVMS  Prev    Current  %Change
> 4     186539  190261   1.99529
> 1     220344  195305   -11.3636
> 
> 
> on 4 Socket/4 Node Power7
> JVMS  Prev    Current  %Change
> 8     56836   57651.1  1.43413
> 1     112970  111351   -1.43312

Why is this better? The largest drop is 11% which seems significant.

Thanks,

	Ingo

  parent reply	other threads:[~2018-09-10  8:39 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-03  6:13 [PATCH 0/6] numa-balancing patches Srikar Dronamraju
2018-08-03  6:13 ` [PATCH 1/6] sched/numa: Stop multiple tasks from moving to the cpu at the same time Srikar Dronamraju
2018-09-10  8:42   ` Ingo Molnar
2018-08-03  6:13 ` [PATCH 2/6] mm/migrate: Use trylock while resetting rate limit Srikar Dronamraju
2018-09-06 11:48   ` Peter Zijlstra
2018-09-10  8:39   ` Ingo Molnar [this message]
2018-08-03  6:13 ` [PATCH 3/6] sched/numa: Avoid task migration for small numa improvement Srikar Dronamraju
2018-09-10  8:46   ` Ingo Molnar
2018-09-12 15:17     ` Srikar Dronamraju
2018-08-03  6:13 ` [PATCH 4/6] sched/numa: Pass destination cpu as a parameter to migrate_task_rq Srikar Dronamraju
2018-08-03  6:14 ` [PATCH 5/6] sched/numa: Reset scan rate whenever task moves across nodes Srikar Dronamraju
2018-09-10  8:48   ` Ingo Molnar
2018-09-12 15:19     ` Srikar Dronamraju
2018-08-03  6:14 ` [PATCH 6/6] sched/numa: Limit the conditions where scan period is reset Srikar Dronamraju
2018-08-21 12:01 ` [PATCH 0/6] numa-balancing patches Srikar Dronamraju
2018-09-06 12:17   ` Peter Zijlstra

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