From: Simon Riggs <simon@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: 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: Mon, 10 Apr 2006 10:26:49 +0100
Message-ID: <1144661209.21409.131.camel@localhost.localdomain> (raw)
In-Reply-To: <17613.1144451138@sss.pgh.pa.us>
References: <C05C3C44.211A5%llonergan@greenplum.com>
<17613.1144451138@sss.pgh.pa.us>
On Fri, 2006-04-07 at 19:05 -0400, Tom Lane wrote:
> 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).
pSeries cache lines are 128 bytes wide, so I'd go straight to 128.
If you're renting all 8 CPUs, I'd drop to 4 and try that instead. With 8
CPUs the contention will vary according to what each CPU is doing at any
one time - when they all hit the contention spot, things will get worse.
The pSeries has good CPUs and great caching, so I'd expect contention to
be somewhat more apparent as a bottleneck.
Best Regards, Simon Riggs
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: simon@2ndquadrant.com, 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: <1144661209.21409.131.camel@localhost.localdomain>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox