Subject: Re: SD still better than CFS for 3d   ?(was Re: 2.6.23-rc1)
From: Kasper Sandberg <lkml@metanurb.dk>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       ck@vds.kolivas.org
In-Reply-To: <20070731085713.GA15136@elte.hu>
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Date: Thu, 02 Aug 2007 01:43:47 +0200
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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

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