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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Lor <Robert.Lor@Sun.COM>
Cc: Tatsuo Ishii <ishii@sraoss.co.jp>
Cc: pgsql-hackers@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: Sun Donated a Sun Fire T2000 to the PostgreSQL
Date: Sun, 23 Jul 2006 21:29:39 -0400
Message-ID: <29920.1153704579@sss.pgh.pa.us> (raw)
In-Reply-To: <44C419BC.1050503@sun.com>
References: <20060617.101521.95879771.t-ishii@sraoss.co.jp>
	<10226.1150511655@sss.pgh.pa.us>
	<20060617.111838.39487910.t-ishii@sraoss.co.jp>
	<20060713.180234.45872055.t-ishii@sraoss.co.jp>
	<8669.1153422118@sss.pgh.pa.us>
	<44C088C8.9050303@sun.com>
	<21889.1153489365@sss.pgh.pa.us>
	<44C195F8.9010409@sun.com>
	<3706.1153678226@sss.pgh.pa.us>
	<44C419BC.1050503@sun.com>

Robert Lor <Robert.Lor@Sun.COM> writes:
> Tom Lane wrote:
>> Yeah, those seem plausible, although the hold time for
>> CheckpointStartLock seems awfully high --- about 20 msec
>> per transaction.  Are you using a nonzero commit_delay?
>> 
> I didn't change commit_delay which defaults to zero.

Hmmm ... AFAICS this must mean that flushing the WAL data to disk
at transaction commit time takes (most of) 20 msec on your hardware.
Which still seems high --- on most modern disks that'd be at least two
disk revolutions, maybe more.  What's the disk hardware you're testing
on, particularly its RPM spec?

			regards, tom lane



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  Subject: Re: Sun Donated a Sun Fire T2000 to the PostgreSQL
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