Horton

Re: [Testperf-general] Re: First set of OSDL Shared Memscalability

Bruce Momjian <pgman@candle.pha.pa.us>

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From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Simon Riggs <simon@2ndquadrant.com>, "Timothy D. Witham" <wookie@osdl.org>, josh@agliodbs.com, pgsql-performance@postgresql.org, testperf-general@pgfoundry.org
Date: 2004-10-15T16:57:35Z
Lists: pgsql-hackers, pgsql-performance 
Tom Lane wrote:
> > I've been thinking about implementing a scheme that helps you decide how
> > big the shared_buffers SHOULD BE, by making the LRU list bigger than the
> > cache itself, so you'd be able to see whether there is beneficial effect in
> > increasing shared_buffers.
> 
> ARC already keeps such a list --- couldn't you learn what you want to
> know from the existing data structure?  It'd be fairly cool if we could
> put out warnings "you ought to increase shared_buffers" analogous to the
> existing facility for noting excessive checkpointing.

Agreed.  ARC already keeps a list of buffers it had to push out recently
so if it needs them again soon it knows its sizing of recent/frequent
might be off (I think).  Anyway, such a log report would be super-cool,
say if you pushed out a buffer and needed it very soon, and the ARC
buffers are already at their maximum for that buffer pool.

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