Re: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)

Kasper Sandberg
2007-08-01T23:47:22Z

On Tue, 2007-07-31 at 10:57 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Tue, 2007-07-31 at 01:46 +0200, Kasper Sandberg wrote:
> >
> > > could perhaps be filesystem related, i have my maildir(extremely
> > > large) on reiserfs, and /home on xfs. what my mail client will do is
> > > download mail, spamasassin it(loading database from home), then it
> > > will put to imap server placing it on reiserfs, and then a "local"
> > > copy in my home.
> >
> > Ooh, do you perchance have PREEMPT_BKL=y?
> >

sorry late response.

nope, i run totally without preemption, i did however test with, it
seemed to not matter in terms of smoothness, but reduced the throughput
slightly.

> > If so, try on another filesystem than reiserfs (or disable
> > PREEMPT_BKL, but that is obviously the lesser of the two choices).
> >
> > Ingo traced a 1+ second latency at my end to BKL priority inversion
> > between tty and reiserfs.
>
> ah, indeed, that makes quite a bit of sense. Almost all of the Reiser3
> code runs under the BKL, and the only other major kernel infrastructure
> that has BKL dependencies is the TTY code. Kasper, as a debugging
> matter, could you try to move that spamassassin workload off into a
> non-Reiser3 filesystem and/or disable PREEMPT_BKL? If that makes a
> noticeable difference (for the better ;) then we can continue figuring
> out what's happening exactly.

the pricess is as this:
mail client fetches mail
mail client invokes spamasassin
if spam -> spam
else filtering
if it matches certain filters, it gets put into my imap server, which is
reiserfs.

> Ingo