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 18:12:39 -0400
Message-ID: <17237.1144447959@sss.pgh.pa.us> (raw)
In-Reply-To: <C05C3088.21195%llonergan@greenplum.com>
References: <C05C3088.21195%llonergan@greenplum.com>
"Luke Lonergan" <llonergan@greenplum.com> writes:
> On 4/7/06 3:02 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
>> On the other hand, we already know that Xeons suck about as badly as
>> can be on that same measure; could the pSeries really be worse?
> I wouldn't be too surprised, but it sounds like it needs a test. Do we have
> a test for this? Is there a contention-prone query stream that we can think
> up?
If you want you could install a pre-8.1 PG and then try one of the
queries that we were using as test cases a year ago for spinlock
investigations. I don't recall details right now but I remember
having posted a pretty trivial test case that would send a
multiprocessor machine into context-swap storm, which sounds a whole
lot like what Gavin is seeing.
I think that 8.1 ought to be relatively free of buffer-manager spinlock
contention, which is why I doubt that test case would be interesting
against 8.1. The interesting question is what else is he seeing
contention for, if it's not the BufMgrLock?
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: <17237.1144447959@sss.pgh.pa.us>
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