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Re: Sun Donated a Sun Fire T2000 to the PostgreSQL

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Lor <Robert(dot)Lor(at)Sun(dot)COM>
Cc: Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org
Subject: Re: Sun Donated a Sun Fire T2000 to the PostgreSQL
Date: 2006-07-21 13:42:45
Message-ID: 21889.1153489365@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Robert Lor <Robert(dot)Lor(at)Sun(dot)COM> writes:
> I ran pgbench and fired up a DTrace script using the lwlock probes we've 
> added, and it looks like BufMappingLock is the most contended lock, but  
> CheckpointStartLocks are held for longer duration!

Those numbers look a bit suspicious --- I'd expect to see some of the
LWLocks being taken in both shared and exclusive modes, but you don't
show any such cases.  You sure your script is counting correctly?
Also, it'd be interesting to count time spent holding shared lock
separately from time spent holding exclusive.

			regards, tom lane

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