linux-kernel - Re: Benchmarking [PATCH v5 00/14] SLUB percpu sheaves

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Message-ID: <f5792407-d2b9-42b3-bc85-ed14eac945ec@paulmck-laptop>
Date: Mon, 15 Sep 2025 05:13:23 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Jan Engelhardt <ej@...i.de>
Cc: Sudarsan Mahendran <sudarsanm@...gle.com>, vbabka@...e.cz,
	Liam.Howlett@...cle.com, cl@...two.org, harry.yoo@...cle.com,
	howlett@...il.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	maple-tree@...ts.infradead.org, rcu@...r.kernel.org,
	rientjes@...gle.com, roman.gushchin@...ux.dev, surenb@...gle.com,
	urezki@...il.com
Subject: Re: Benchmarking [PATCH v5 00/14] SLUB percpu sheaves

On Mon, Sep 15, 2025 at 09:51:25AM +0200, Jan Engelhardt wrote:
> 
> On Saturday 2025-09-13 02:09, Sudarsan Mahendran wrote:
> >
> >Summary of the results:
> >
> >- Significant change (meaning >10% difference
> >  between base and experiment) on will-it-scale
> >  tests in AMD.
> >
> >Summary of AMD will-it-scale test changes:
> >
> >Number of runs : 15
> >Direction      : + is good
> 
> If STDDEV grows more than mean, there is more jitter,
> which is not "good".

This is true.  On the other hand, the mean grew way more in absolute
terms than did STDDEV.  So might this be a reasonable tradeoff?

Of course, if adjustments can be made to keep the increase in mean while
keeping STDDEV low, that would of course be even better.

							Thanx, Paul

> >|            | MIN        | MAX        | MEAN       | MEDIAN     | STDDEV     |
> >|:-----------|:-----------|:-----------|:-----------|:-----------|:-----------|
> >| brk1_8_processes
> >| BASE       | 7,667,220  | 7,705,767  | 7,682,782  | 7,676,211  | 12,733     |
> >| TEST       | 9,477,395  | 10,053,058 | 9,878,753  | 9,959,360  | 182,014    |
> >| %          | +23.61%    | +30.46%    | +28.58%    | +29.74%    | +1,329.46% |
> >
> >| mmap2_256_processes
> >| BASE       | 7,483,929  | 7,532,461  | 7,491,876  | 7,489,398  | 11,134     |
> >| TEST       | 11,580,023 | 16,508,551 | 15,337,145 | 15,943,608 | 1,489,489  |
> >| %          | +54.73%    | +119.17%   | +104.72%   | +112.88%   | +13,276.75%|
>