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Subject: Re: svn commit: r312666 - stable/10/sys/kern
To: Andriy Gapon <avg@FreeBSD.org>, Bruce Evans <brde@optusnet.com.au>
References: <201701230834.v0N8Ypnu011042@repo.freebsd.org>
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Cc: src-committers@FreeBSD.org, svn-src-all@FreeBSD.org,
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From: Eric van Gyzen <vangyzen@FreeBSD.org>
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Date: Mon, 23 Jan 2017 12:12:14 -0600
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On 01/23/2017 10:03, Andriy Gapon wrote:
> On 23/01/2017 15:34, Bruce Evans wrote:
>> What is a good benchmark for showing that the fix helps?
> 
> Honestly, I do not know.  We ran into a pathology where a thread was not getting
> scheduled for a long time after being preempted while in a critical section (so
> the actual preemption was a voluntary switch when exiting the critical section).
>  I am not sure what kind of a synthetic benchmark or a test case would readily
> demonstrate the problem.

I submitted r270423, which introduced the bug Andriy just fixed.  I'm
already setting up the performance test that I used for that change.
It's a macro-benchmark of a commercial product, so I can't elaborate on
details, but at least I can give a thumb indication in the style of a
Roman Dictator.

Eric