linux-kernel - Re: RFT: updatedb "morning after" problem [was: Re: -mm merge plans for 2.6.23]

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Message-ID: <20070726102730.GA31894@elte.hu>
Date:	Thu, 26 Jul 2007 12:27:30 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Frank Kingswood <frank@...gswood-consulting.co.uk>,
	Andi Kleen <andi@...stfloor.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Ray Lee <ray-lk@...rabbit.org>,
	Jesper Juhl <jesper.juhl@...il.com>,
	ck list <ck@....kolivas.org>, Paul Jackson <pj@....com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: RFT: updatedb "morning after" problem [was: Re: -mm merge
	plans for 2.6.23]


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> > > > ( we _do_ want to baloon the dentry cache otherwise - for things like 
> > > >   "find" - having a fast VFS is important. But known-use-once things 
> > > >   like the daily updatedb job can clearly be annotated properly. )
> > > 
> > > Mutter.  /proc/sys/vm/vfs_cache_pressure has been there for what, 
> > > three years?  Are any distros raising it during the updatedb run yet?
> > 
> > but ... that's system-wide, and the 'dont baloon the dcache' is only a 
> > property of updatedb.
> 
> Sure, but it's practical, isn't it?  Who runs (and cares about) 
> vfs-intensive workloads during their wee-small-hours updatedb run?

there's another side-effect: it likely results in the zapping of 
thousands of dentries that were cached nicely before. So we might 
exchange 'all my apps are swapped out' experience with 'all file access 
is slow'. The latter is _probably_ still an improvement over the 
balooning, but i'm not sure. What we _really_ want is an updatedb that 
does not disturb the dcache.

	Ingo
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