From: Greg Smith <greg@2ndquadrant.com>
To: Ivan Voras <ivoras@freebsd.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: CPUs for new databases
Date: Wed, 27 Oct 2010 15:58:46 -0400
Message-ID: <4CC88476.7010804@2ndquadrant.com> (raw)
In-Reply-To: <ia7r55$5ih$1@dough.gmane.org>
References: <4CC6CFAA.10107@one.com>
<AANLkTi=ScGQiHB2ch+C_+K14TgjaO_3+x0+28QOFYeUU@mail.gmail.com>
<4CC73FEF.9020805@agliodbs.com>
<m3ocagplgf.fsf@jhcloos.com>
<ia7r55$5ih$1@dough.gmane.org>
Ivan Voras wrote:
> FWIW, yes - once the IO is fast enough or not necessary (e.g. the
> read-mostly database fits in RAM), RAM bandwidth *is* the next
> bottleneck and it really, really can be observed in actual loads.
This is exactly what I've concluded, after many rounds of correlating
memory speed tests with pgbench tests against in-RAM databases. And
it's the reason why I've written the stream-scaling utility and been
collecting test results from as many systems as possible. That seemed
to get dismissed upthread as not being the answer the poster was looking
for, but I think you have to get a handle on that part before the rest
of the trivia involved even matters.
I have a bunch more results that have been flowing in that I need to
publish there soon. Note that there is a bug in stream-scaling where
sufficiently large systems can hit a compiler problem where it reports
"relocation truncated to fit: R_X86_64_PC32 against `.bss'". I have two
of those reports and am working on resolving.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
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To: pgsql-performance@postgresql.org
Cc: greg@2ndquadrant.com, ivoras@freebsd.org
Subject: Re: CPUs for new databases
In-Reply-To: <4CC88476.7010804@2ndquadrant.com>
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