From: Ian Westmacott <ianw@intellivid.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: cost-based vacuum
Date: Wed, 13 Jul 2005 14:40:36 -0400
Message-ID: <1121280036.13208.8.camel@spectre.intellivid.com> (raw)
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On Wed, 2005-07-13 at 11:55, Simon Riggs wrote:
> On Tue, 2005-07-12 at 13:50 -0400, Ian Westmacott wrote:
> > It appears not to matter whether it is one of the tables
> > being written to that is ANALYZEd. I can ANALYZE an old,
> > quiescent table, or a system table and see this effect.
>
> Can you confirm that this effect is still seen even when the ANALYZE
> doesn't touch *any* of the tables being accessed?
Yes.
> > - this is a dual Xeon.
>
> Is that Xeon MP then?
Yes.
> > - Looking at oprofile reports for 10-minute runs of a
> > database-wide VACUUM with vacuum_cost_delay=0 and 1000,
> > shows the latter spending a lot of time in LWLockAcquire
> > and LWLockRelease (20% each vs. 2%).
>
> Is this associated with high context switching also?
Yes, it appears that context switches increase up to 4-5x
during cost-based ANALYZE.
--Ian
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To: pgsql-performance@postgresql.org
Cc: ianw@intellivid.com, simon@2ndquadrant.com, tgl@sss.pgh.pa.us
Subject: Re: cost-based vacuum
In-Reply-To: <1121280036.13208.8.camel@spectre.intellivid.com>
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