Roy Schestowitz wrote:
> Linux: Replacing atime With relatime
>
> ,----[ Quote ]
> | Ingo Molnar stressed the significance of fixing this performance issue,
> | "I cannot over-emphasize how much of a deal it is in practice. Atime
> | updates are by far the biggest IO performance deficiency that Linux has
> | today. Getting rid of atime updates would give us more everyday Linux
> | performance than all the pagecache speedups of the past 10 years,
> | _combined_." He submitted some patches to improve relatime...
> `----
>
> http://kerneltrap.org/node/14148
>
Isn't it odd, that a thing can be on the system right from the start and you
don't tend to think of it being a potential problem. By force of habit you
tend to change the attributes of a database directory so that atime isn't
recorded, but don't tend to think about why you do that anymore, you have
simply done it for so long that it is hard to stop, like picking your nose.
But the list of timings in that post show no_atime as quite a significant
time saver, not really for servers with medium to low resource use, nor I
would think for desktops. But as it says in the 'man' page very likely that
laptops would benefit for changing this attribute.
Heavily used servers it could be very significant.
So what problems might there be if we didn't have atime.
Well 'find' is the most obvious place, but really we are much more likely to
search for modified or created files.
There is a little thing I personally did for quite some time, I used to run
a script that gives me a list of all user's files accessed out of work
hours, because I worked at a place once where the security staff knew a
couple of user passwords and would fill their long evenings having a nose
around.
Other than something in those lines I can not really think of a place where
atime is actually used. (you watch, bet lots of you come up with hundreds
of places we all use it daily without realising it).
I suppose a quick way to see what benefits each of us might get from turning
atime off, is to turn it off on the buisiest part of our own directories
first, something like this,
chattr -R +A $HOME/Databases
It can only be a relative timing really, feels faster to you the user,
because the how busy the system is at different times is significant in
this. But may be worth experimenting with.
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