Re: Clock sweep not caching enough B-Tree leaf pages?

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Greg Stark <stark(at)mit(dot)edu>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Clock sweep not caching enough B-Tree leaf pages?
Date: 2014-04-17 18:54:21
Message-ID: 20140417185421.GN2556@tamriel.snowman.net
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* Andres Freund (andres(at)2ndquadrant(dot)com) wrote:
> > Note that if we somehow come up with a page replacement algorithm that tends
> > to evict pages that are in the OS cache, we have effectively solved the
> > double buffering problem. When a page is cached in both caches, evicting it
> > from one of them eliminates the double buffering. Granted, you might prefer
> > to evict it from the OS cache instead, and such an algorithm could be bad in
> > other ways. But if a page replacement algorithm happens avoid double
> > buffering, that's a genuine merit for that algorithm.
>
> I don't think it's a good idea to try to synchronize algorithms with the
> OSs. There's so much change about the caching logic in e.g. linux that
> it won't stay effective for very long.

There's also more than one OS...

Thanks,

Stephen

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