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Message-ID: <468DAFD5.30002@Yahoo.com>
Date: Thu, 05 Jul 2007 22:58:29 -0400
From: Jan Wieck <JanWieck@Yahoo.com>
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To: Tom Lane <tgl@sss.pgh.pa.us>
CC: PostgreSQL Development <pgsql-hackers@postgresql.org>
Subject: Re: usleep feature for pgbench
References: <468D42B3.4010701@Yahoo.com> <20905.1183664046@sss.pgh.pa.us>
	<468D57F3.7030405@Yahoo.com> <21985.1183671014@sss.pgh.pa.us>
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On 7/5/2007 5:30 PM, Tom Lane wrote:
> Jan Wieck <JanWieck@Yahoo.com> writes:
>> I think I've coded it in a way that if one doesn't use the \usleep 
>> command at all, it will never even call gettimeofday() and use a NULL 
>> timeout in select() as it used to.
> 
> Did you check that the observed performance for non-usleep-using scripts
> didn't change?  If this extra overhead causes a reduction in reported
> TPS rates it would make it hard to compare older and newer tests.

Given pgbench's unpredictability of results ... lets see.

I ran

     dropdb x
     createdb x
     pgbench -i -s10 x
     psql -c 'checkpoint' x
     sleep 1
     psql -c 'checkpoint' x
     pgbench -s10 -c5 -t10000 x
     pgbench -s10 -c5 -t10000 x
     pgbench -s10 -c5 -t10000 x

Original pgbench reported 39, 37 and 33 TPS. Having my patch applied it 
reported 40, 38 and 33 TPS. Inserting a "\usleep 1" after the update to 
accounts of a default equivalent script changed those numbers to 40, 37 
and 33. I interpret that as "does not change observed performance".

> 
> Other than that I've got no objection to it.

Will be committed after adjusting the README.


Jan

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