Re: [PATCH 00/23] per device dirty throttling -v8

Ingo Molnar
2007-08-04T20:28:30Z

* Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> Either change is a big user/kernel interface change and no major
> vendor targets desktop as primary market so I'm not suprised they
> haven't done this. [...]

earlier in the thread it was claimed that Ubuntu is now defaulting to
noatime+nodiratime, and has done so for several months. Could be one of
the reasons why:

http://www.google.com/trends?q=fedora%2C+ubuntu

> People just need to know about the performance differences - very few
> realise its more than a fraction of a percent. I'm sure Gentoo will
> use relatime the moment anyone knows its > 5% 8)

noatime,nodiratime gave 50% of wall-clock kernel rpm build performance
improvement for Dave Jones, on a beefy box. Unless i misunderstood what
you meant under 'fraction of a percent' your numbers are _WAY_ off.
Atime updates are a _huge everyday deal_, from laptops to servers.
Everywhere on the planet. Give me a Linux desktop anywhere and i can
tell you whether it has atimes on or off, just by clicking around and
using apps (without looking at the mount options). That's how i notice
it that i forgot to turn off atime on any newly installed system - the
system has weird desktop lags and unnecessary disk trashing.

> [...] Ext3 currently is a standards compliant file system. Turn off
> atime and its very non standards compliant, turn to relatime and its
> not standards compliant but nobody will break (which is good)

come on! Any standards testsuite needs tons of tweaks to the system to
run through to completion. Mounting the filesystem atime will just be
one more item in the long list of (mostly silly) 'needed for standards
compliance' items (most of which nobody configures). What matters are
the apps, and nary any app depends on atime, and those people who depend
on them can turn on atime just fine. (it's the same as for extended
attributes for example - and attributes are infinitely _more_ useful
than atime.)

Ingo