From: Con Kolivas <kernel@kolivas.org>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/33] Adaptive read-ahead V12
Date: Sat, 27 May 2006 10:08:41 +1000
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Cc: Folkert van Heusden <folkert@vanheusden.com>, Andi Kleen <ak@suse.de>,
       Andrew Morton <akpm@osdl.org>, wfg@mail.ustc.edu.cn, mstone@mathom.us
References: <348469535.17438@ustc.edu.cn> <20060526235436.GD4294@vanheusden.com> <200605271000.12061.kernel@kolivas.org>
In-Reply-To: <200605271000.12061.kernel@kolivas.org>
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On Saturday 27 May 2006 10:00, Con Kolivas wrote:
> On Saturday 27 May 2006 09:54, Folkert van Heusden wrote:
> > > > These are nice-looking numbers, but one wonders.  If optimising
> > > > readahead makes this much difference to postgresql performance then
> > > > postgresql should be doing the readahead itself, rather than relying
> > > > upon the kernel's ability to guess what the application will be doing
> > > > in the future.  Because surely the database can do a better job of
> > > > that than the kernel.
> > >
> > > With that argument we should remove all readahead from the kernel?
> > > Because it's already trying to guess what the application will do.
> > > I suspect it's better to have good readahead code in the kernel
> > > than in a zillion application.
> >
> > Maybe a pluggable read-ahead system could be implemented.
>
> Pluggable anything is unpopular with Linus and other maintainers. See
> pluggable cpu scheduler and pluggable page replacement policy (vm)
> patchsets.

Sorry I should have been clearer. The belief is that certain infrastructure 
components do not benefit from a pluggable framework, and readeahead probably 
comes under that description. It's not like Linus was implying we should only 
have one filesystem for example, since filesystems are afterall pluggable 
features.

-- 
-ck
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