Re: [PATCHES] ARC Memory Usage analysis

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jan Wieck <JanWieck@Yahoo.com>
Cc: Simon Riggs <simon@2ndquadrant.com>, pgsql-patches@postgresql.org, pgsql-hackers@postgresql.org, josh@agliodbs.com
Date: 2004-10-22T20:45:51Z
Lists: pgsql-hackers, pgsql-performance
Jan Wieck <JanWieck@Yahoo.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