linux-kernel - Re: updatedb

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Date:	Thu, 26 Jul 2007 13:23:03 +0700
From:	"Andika Triwidada" <andika@...il.com>
To:	"Rene Herman" <rene.herman@...il.com>
Cc:	"Robert Deaton" <false.hopes@...il.com>,
	linux-kernel@...r.kernel.org, "ck list" <ck@....kolivas.org>,
	linux-mm@...ck.org
Subject: Re: updatedb

On 7/26/07, Rene Herman <rene.herman@...il.com> wrote:
> On 07/25/2007 07:15 PM, Robert Deaton wrote:
>
> > On 7/25/07, Rene Herman <rene.herman@...il.com> wrote:
>
> >> And there we go again -- off into blabber-land. Why does swap-prefetch
> >> help updatedb? Or doesn't it? And if it doesn't, why should anyone
> >> trust anything else someone who said it does says?
>
> > I don't think anyone has ever argued that swap-prefetch directly helps
> > the performance of updatedb in any way
>
> People have argued (claimed, rather) that swap-prefetch helps their system
> after updatedb has run -- you are doing so now.
>
> > however, I do recall people mentioning that updatedb, being a ram
> > intensive task, will often cause things to be swapped out while it runs
> > on say a nightly cronjob.
>
> Problem spot no. 1.
>
> RAM intensive? If I run updatedb here, it never grows itself beyond 2M. Yes,
> two. I'm certainly willing to accept that me and my systems are possibly not
> the reference but assuming I'm _very_ special hasn't done much for me either
> in the past.

Might be insignificant, but updatedb calls find (~2M) and sort (~26M).
Definitely not RAM intensive though (RAM is 1GB).

>
> The thing updatedb does do, or at least has the potential to do, is fill
> memory with cached inodes/dentries but Linux does not swap to make room for
> caches. So why will updatedb "often cause things to be swapped out"?
>

[ snip ]
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