Disabling atime
Ralf Corsepius
rc040203 at freenet.de
Fri Aug 10 13:09:11 UTC 2007
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.
Ralf
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