Disabling atime

[Josh Boyer]

On Fri, 10 Aug 2007 15:09:11 +0200
Ralf Corsepius <rc040203 at freenet.de> wrote:

> On Fri, 2007-08-10 at 07:59 -0400, James Hubbard wrote:
> > On 8/9/07, Ralf Corsepius <rc040203 at freenet.de> wrote:
> > > IMO, disabling atime by default, just because 99% of
> > > applications, don't use it, is short-sighted. It basically
> > > ditches a fundamental feature of unix filessystems and converts
> > > there behavior to "DOS'ish".
> > 
> > If it's such a fundamental feature that should be kept around, why
> > have NFS optimization documents always recommended disabling atime
> > updates especially on servers where there is a lot of throughput?
> I don't know.
> 
> > Just because it's a fundamental feature doesn't mean that it has to
> > be used. Fundamentally, my CPU can run at 2GHz all of the time that
> > doesn't mean that it should.  If 99% of the applications can do
> > without it and probably 99% of the people can as well, why not go
> > ahead and get disable it.
> That's what people call "arrogance of the masses". Let's kill that 1%,
> if 99% don't care!
> 
> <sarcasm>
> It's the same argument why people argue against utf-8, work as root
> (don't need uid/gids) and don't want SELinux? 
> 
> Let's remove all of this from the kernel, single seat/single user
> systems don't need all this at all.
> </sarcasm>
> 
> > Those that need atime will eventually figure out how to turn it on.
> > The potential for a better user experience as well possible power
> > savings seems to outweigh the fundamental feature argument.
> 
> A friend of mine experimented with atime/noatime yesterday:
> 
> These were his results:
> 
> Test case: A heavy weight compiler-job
> 
> Default /etc/fstab
>   real    5m18.226s
>   user    4m44.557s
>   sys     1m17.193s
> User+Sys: 365.750
> 
> Rebooted -- all filesystems noatime,nodiratime
>   real    5m4.256s
>   user    4m36.841s
>   sys     1m8.364s
> User+Sys: 346.750
> 
> new / old = .9465
> 
> [Fedora-7, i386 on an AMD Athlon(tm) 64 X2 Dual Core Processor 3800+]
> 
> Way off from the figures the proponents of notime are reporting.

Well... a heavy compile job isn't going to reflect that much because
you're writing to the disk anyway.

Perhaps try doing a 'find / -exec cat {} > /dev/null \;' with and without atime.

josh