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Re: [PATCHES] ARC Memory Usage analysis

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jan Wieck <JanWieck(at)Yahoo(dot)com>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>,pgsql-patches(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org,josh(at)agliodbs(dot)com
Subject: Re: [PATCHES] ARC Memory Usage analysis
Date: 2004-10-22 20:45:51
Message-ID: 18764.1098477951@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patchespgsql-performance
Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
> What do you think about my other theory to make C actually 2x effective 
> cache size and NOT to keep T1 in shared buffers but to assume T1 lives 
> in the OS buffer cache?

What will you do when initially fetching a page?  It's not supposed to
go directly into T2 on first use, but we're going to have some
difficulty accessing a page that's not in shared buffers.  I don't think
you can equate the T1/T2 dichotomy to "is in shared buffers or not".

You could maybe have a T3 list of "pages that aren't in shared buffers
anymore but we think are still in OS buffer cache", but what would be
the point?  It'd be a sufficiently bad model of reality as to be pretty
much useless for stats gathering, I'd think.

			regards, tom lane

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