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Date:      Mon, 23 Jan 2017 12:12:14 -0600
From:      Eric van Gyzen <vangyzen@FreeBSD.org>
To:        Andriy Gapon <avg@FreeBSD.org>, Bruce Evans <brde@optusnet.com.au>
Cc:        src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, svn-src-stable@FreeBSD.org, svn-src-stable-10@FreeBSD.org
Subject:   Re: svn commit: r312666 - stable/10/sys/kern
Message-ID:  <d0970738-8eb7-8a81-453f-199f11fd2e39@FreeBSD.org>
In-Reply-To: <49838a2b-c628-da8c-4c9c-4a66c83119f8@FreeBSD.org>
References:  <201701230834.v0N8Ypnu011042@repo.freebsd.org> <20170124002712.Q903@besplex.bde.org> <49838a2b-c628-da8c-4c9c-4a66c83119f8@FreeBSD.org>

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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



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