Re: CONFIG_PREEMPT and server workloads

[Takashi Iwai <tiwai@suse.de>]

At Thu, 18 Mar 2004 22:07:41 -0500,
Eric St-Laurent wrote:
> 
> On Thu, 2004-03-18 at 10:28, Takashi Iwai wrote:
> 
> > in my case with reiserfs, i got 0.4ms RT-latency with my test suite
> > (with athlon 2200+).
> > 
> > there is another point to be fixed in the reiserfs journal
> > transaction.  then you'll get 0.1ms RT-latency without preemption.
> 
> Are you talking about the following patch recently merged in Linus tree?
> 
> [PATCH] resierfs: scheduling latency improvements
> http://linus.bkbits.net:8080/linux-2.5/cset@40571b49jtE7PzOtsXjBx65-GoDijg

i've tested the suse kernel, so the patch above was already in it.
i'm not sure whether mm tree already includes the all relevant
fixes... Chris?

what i wrote above about is loops in do_journal_end().  but i can't
tell you surely unless i test the mm kernel again.

> I'm interested to try any patch you might have to help reduce latency
> with reiserfs.

AFAIK, even only the fix of mpage_writepages() will reduce the latency
very much.  please give a try.


Takashi