Horton

Re: MMAP Buffers

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Radosław Smogura <rsmogura@softperience.eu>
Cc: Peter Eisentraut <peter_e@gmx.net>, Greg Stark <gsstark@mit.edu>, Robert Haas <robertmhaas@gmail.com>, Greg Smith <greg@2ndquadrant.com>, Joshua Berkus <josh@agliodbs.com>, Andrew Dunstan <andrew@dunslane.net>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, PG Hackers <pgsql-hackers@postgresql.org>
Date: 2011-04-16T23:35:45Z
Lists: pgsql-hackers 
=?utf-8?q?Rados=C5=82aw_Smogura?= <rsmogura@softperience.eu> writes:
> No, no, no :) I wanted to do this, but from above reason I skipped it. I swap 
> VM pages, I do remap, in place where the shared buffer was I put mmaped page, 
> and in place where mmaped page was I put shared page (in certain cases, which 
> should be optimized by e. g. read for update, for initial read of page in 
> process I directly points to shared buffer), it can be imagined as I affects 
> TLB. This what I call "VM swap" is remapping, so I don't change pointers, I 
> change only where this pointers points in physical memory, preserving same 
> pointer in Virtual Memory.

... Huh?  Are you saying that you ask the kernel to map each individual
shared buffer separately?  I can't believe that's going to scale to
realistic applications.

			regards, tom lane