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 18:02:55 -0400
Message-ID: <17108.1144447375@sss.pgh.pa.us> (raw)
In-Reply-To: <C05C2CB7.2118D%llonergan@greenplum.com>
References: <C05C2CB7.2118D%llonergan@greenplum.com>
"Luke Lonergan" <llonergan@greenplum.com> writes:
> That said, I find typical memory bandwidth for the P4 in applications is
> limited at about 2GB/s. See here for more detail:
> http://www.cs.virginia.edu/stream/standard/Bandwidth.html> In fact, looking at the results there, the IBM 650m2 only gets 6GB/s
> on all 8 CPUs. I wouldn't be surprised if the strange L3 cache
> architecture of the IBM 650 is holding it back from streaming memory
> access efficiently.
Given Gavin's latest report, I'm wondering how much the IBM slows down
when a spinlock operation is involved. If the memory architecture isn't
good about supporting serialized access to memory, that gaudy sounding
bandwidth number might have little to do with PG's real-world behavior.
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?
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: <17108.1144447375@sss.pgh.pa.us>
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