linux-kernel - Re: [PATCH v4] relatime: Make relatime smarter

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Message-ID: <20081202164631.GA25548@parisc-linux.org>
Date:	Tue, 2 Dec 2008 09:46:31 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Karel Zak <kzak@...hat.com>
Cc:	Jamie Lokier <jamie@...reable.org>,
	Matthew Garrett <mjg@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	mingo@...hat.com, val.henson@...il.com
Subject: Re: [PATCH v4] relatime: Make relatime smarter

On Tue, Dec 02, 2008 at 12:10:25PM +0100, Karel Zak wrote:
> On Fri, Nov 28, 2008 at 06:40:55AM -0700, Matthew Wilcox wrote:
> > On Fri, Nov 28, 2008 at 11:18:09AM +0000, Jamie Lokier wrote:
> > > Matthew Garrett wrote:
> > > > The time between atime updates can be configured at boot
> > > > with the relatime_interval kernel argument, or at runtime through a sysctl.
> > > 
> > > Shouldn't it be a per-mount value, with defaults coming from the sysctl?
> > 
> > Perhaps a more sensible question would be "Why make it configurable at
> 
>  this is GNOME-mentality :-)

Yes, I frequently pal around with terrorists.

> > all?"  What's wrong with hardcoding 24 hours?  Or, to put it another
> > way, who wants to change it from 24 hours, and why?
> 
>  Why do you think that 24 hours is the right default value? Do you
>  have any logical argument for this setting?

Once a day seems like a good value to me.  It's a good human being
timescale and still cuts down the number of atime updates by a lot.

If somebody really cares, they could graph the relatime_update value
against number of writes performed in a given period and determine a
better cutoff.  I can think of a hundred better ways to spend my time
though.

Good job of not answering the question, by the way.  Why _not_ 24 hours?

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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