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Date:      Wed, 24 Mar 2004 18:40:51 +0000
From:      Colin Percival <colin.percival@wadham.ox.ac.uk>
To:        Sean Chittenden <seanc@FreeBSD.org>
Cc:        Jason Coene <jcoene@gotfrag.com>
Subject:   Re: cvs commit: src/sys/kern sysv_sem.c
Message-ID:  <6.0.1.1.1.20040324183111.043c2228@imap.sfu.ca>
In-Reply-To: <D39C9A62-7DBB-11D8-B2DF-000A95C705DC@FreeBSD.org>
References:  <200403170937.i2H9bDvO033177@repoman.freebsd.org> <D39C9A62-7DBB-11D8-B2DF-000A95C705DC@FreeBSD.org>

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At 17:51 24/03/2004, Sean Chittenden wrote:
>>  FreeBSD src repository
>>
>>  Modified files:
>>    sys/kern             sysv_sem.c
>>  Log:
>>  Adjust the number of processes waiting on a semaphore properly if we're
>>  woken up in the middle of sleeping.
>
>Have you read the thread on performance@ regarding semaphore performance problems for PostgreSQL?  Do you think this has any bearing on that problem?  -sc

I hadn't seen the thread on performance@ until now, but it sounds like this
is very likely related -- this bug would result in processes not being woken
up when a semaphore becomes free.

Jason, could you update your src/sys/kern/sysv_sem.c to the latest revision
(1.69), build a new kernel, and see if the problem goes away?

Colin Percival




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