Message-ID: <4C87E3A6.8060800@2ndquadrant.com>
Date: Wed, 08 Sep 2010 15:27:34 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: David Kerr <dmk@mr-paradox.net>, pgsql-performance@postgresql.org
Subject: Re: pgbench could not send data to client: Broken pipe
References: <20100908174629.GD40339@mr-paradox.net>
	<8037.1283973026@sss.pgh.pa.us>
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Tom Lane wrote:
> As of the 9.0 release, it's possible to run pgbench in a "multi thread"
> mode, and if you forced the subprocess rather than thread model it looks
> like the select() limit would be per subprocess rather than global.
> So I think you could get above the FD_SETSIZE limit with a bit of
> hacking if you were using 9.0's pgbench.  No chance with 8.3 though.
>   

I believe David can do this easily enough by compiling a 9.0 source code 
tree with the "--disable-thread-safety" option.  That's the simplest way 
to force the pgbench client to build itself using the multi-process 
model, rather than the multi-threaded one.

It's kind of futile to run pgbench simulating much more than a hundred 
or two clients before 9.0 anyway.  Without multiple workers, you're 
likely to just run into the process switching limitations within pgbench 
itself rather than testing server performance usefully.  I've watched 
the older pgbench program fail to come close to saturating an 8 core 
server without running into its own limitations first.

You might run a 9.0 pgbench client against an 8.3 server though, if you 
did the whole thing starting from pgbench database initialization over 
again--the built-in tables like "accounts" changed to "pgbench_accounts" 
in 8.4.  That might work, can't recall any changes that would prevent 
it; but as I haven't tested it yet I can't say for sure.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us