Re: O_DIRECT in freebsd - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: O_DIRECT in freebsd
Date
Msg-id 200306230418.h5N4Iu224181@candle.pha.pa.us
Whole thread Raw
In response to Re: O_DIRECT in freebsd  (Sean Chittenden <sean@chittenden.org>)
List pgsql-hackers
Sean Chittenden wrote:
> > > 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.  :-]

OK, that's 4 of 15 platforms.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
Pennsylvania19073
 


pgsql-hackers by date:

Previous
From: "Christopher Kings-Lynne"
Date:
Subject: Re: Two weeks to feature freeze
Next
From: The Hermit Hacker
Date:
Subject: Re: Two weeks to feature freeze