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

Andrew Morton
2007-08-04T16:52:47Z

On Sat, 4 Aug 2007 18:37:33 +0200 Ingo Molnar <mingo@elte.hu> wrote:

>
> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> > > hm, it turns out that it's due to vim doing an occasional fsync not
> > > only on writeout, but during normal use too. "set nofsync" in the
> > > .vimrc solves this problem.
> >
> > Yes, that's independent. The fact is, ext3 *sucks* at fsync. I hate
> > hate hate it. It's totally unusable, imnsho.
>
> yeah, it's really ugly. But otherwise i've got no real complaint about
> ext3 - with the obligatory qualification that "noatime,nodiratime" in
> /etc/fstab is a must. This speeds up things very visibly - especially
> when lots of files are accessed. It's kind of weird that every Linux
> desktop and server is hurt by a noticeable IO performance slowdown due
> to the constant atime updates,

Not just more IO: it will cause great gobs of blockdev pagecache to remain
in memory, too.

> while there's just two real users of it:
> tmpwatch [which can be configured to use ctime so it's not a big issue]
> and some backup tools. (Ok, and mail-notify too i guess.) Out of tens of
> thousands of applications. So for most file workloads we give Windows a
> 20%-30% performance edge, for almost nothing. (for RAM-starved kernel
> builds the performance difference between atime and noatime+nodiratime
> setups is more on the order of 40%)
>
> Ingo