Re: Clock sweep not caching enough B-Tree leaf pages? - Mailing list pgsql-hackers

From Stephen Frost
Subject Re: Clock sweep not caching enough B-Tree leaf pages?
Date
Msg-id 20140417190007.GO2556@tamriel.snowman.net
Whole thread Raw
In response to Re: Clock sweep not caching enough B-Tree leaf pages?  (Merlin Moncure <mmoncure@gmail.com>)
Responses Re: Clock sweep not caching enough B-Tree leaf pages?  (Merlin Moncure <mmoncure@gmail.com>)
Re: Clock sweep not caching enough B-Tree leaf pages?  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
* Merlin Moncure (mmoncure@gmail.com) wrote:
> I doubt that's necessary though -- if the postgres caching algorithm
> improves such that there is a better tendency for hot pages to stay in
> s_b,  Eventually the O/S will deschedule the page for something else
> that needs it.   In other words, otherwise preventable double
> buffering is really a measurement of bad eviction policy because it
> manifests in volatility of frequency accessed pages.

I wonder if it would help to actually tell the OS to read in buffers
that we're *evicting*...  On the general notion that if the OS already
has them buffered then it's almost a no-op, and if it doesn't and it's
actually a 'hot' buffer that we're gonna need again shortly, the OS will
have it.

In other words, try to make the OS more like a secondary cache to ours
by encouraging it to cache things we're evicting.
Thanks,        Stephen

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