Re: [HACKERS] Sun Donated a Sun Fire T2000 to the PostgreSQL

From: Sven Geisler <sgeisler(at)aeccom(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Lor <Robert(dot)Lor(at)Sun(dot)COM>, Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org
Subject: Re: [HACKERS] Sun Donated a Sun Fire T2000 to the PostgreSQL
Date: 2006-07-21 14:59:49
Message-ID: 44C0EBE5.8010508@aeccom.com
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Hi,

Tom Lane schrieb:
> 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.

Is there a test case which shows the contention for this full cached
tables? It would be nice to have measurable numbers like context
switches and queries per second.

Sven.

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