From: Tom Lane <tgl@sss.pgh.pa.us>
To: Luke Lonergan <llonergan@greenplum.com>
Cc: Gavin Hamill <gdh@laterooms.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: pg 8.1.3, AIX, huge box, painfully slow.
Date: Fri, 07 Apr 2006 19:05:38 -0400
Message-ID: <17613.1144451138@sss.pgh.pa.us> (raw)
In-Reply-To: <C05C3C44.211A5%llonergan@greenplum.com>
References: <C05C3C44.211A5%llonergan@greenplum.com>
"Luke Lonergan" <llonergan@greenplum.com> writes:
> On 4/7/06 3:27 PM, "Gavin Hamill" <gdh@laterooms.com> wrote:
>> 278774: __semop(15728650, 0x0FFFFFFFFFFF7E80, 1) = 0
>> 155712: __semop(15728650, 0x0FFFFFFFFFFF5920, 1) = 0
>> 278774: __semop(15728649, 0x0FFFFFFFFFFF6F10, 1)
> Seems like you're hitting a very small target in RAM with these semop calls.
IIRC the address passed to semop() in our code is always a local struct
on the stack, so that's a bit of a red herring --- there won't be
cross-processor contention for that.
It's plausible though that we are seeing contention across members of
the LWLock array, with the semop storm just being a higher-level symptom
of the real hardware-level problem. You might try increasing
LWLOCK_PADDED_SIZE to 64 or even 128, see
src/backend/storage/lmgr/lwlock.c (this is something that does exist in
8.1, so it'd be easy to try).
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, llonergan@greenplum.com, gdh@laterooms.com
Subject: Re: pg 8.1.3, AIX, huge box, painfully slow.
In-Reply-To: <17613.1144451138@sss.pgh.pa.us>
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