From: | Sean Chittenden <sean(at)chittenden(dot)org> |
---|---|
To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | "Jim C(dot) Nasby" <jim(at)nasby(dot)net>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: O_DIRECT in freebsd |
Date: | 2003-06-23 04:13:37 |
Message-ID: | 20030623041337.GP97131@perrin.int.nxad.com |
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Thread: | |
Lists: | pgsql-hackers |
> > Nor could it ever be a win unless the cache was populated via
> > O_DIRECT, actually. Big PG cache == 2 extra copies of data, once
> > in the kernel and once in PG. Doing caching at the kernel level,
> > however means only one copy of data (for the most part). Only
> > problem with this being that it's not always that easy or an
> > option to reconfig a kernel to have a bigger FS cache. That said,
> > tripple copying a chunk of mem is generally faster than even a
> > single disk read. If PostgreSQL ever wanted to have a platform
> > agnostic way of doing efficient caching, it'd likely have to be in
> > the userland and would require the use of O_DIRECT.
>
> Actually, I think of O_DIRECT as platform-dependent.
FreeBSD, IRIX, and AIX, implement it, and ... *smiles with pride*
looks like Linux does too given the number of security vulnerabilities
associated with the call. :-]
-sc
--
Sean Chittenden
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