Re: Kernel 2.4.x and 2.4.1-preX - Higher latency then 2.2.xkernels?

Shawn Starr
2001-01-27T08:04:58Z

Applying now.

Andrew Morton wrote:

> Shawn,
>
> I've pretty much completed the low-latency patch against reiserfs.
> It seems to be a little more latency-prone than ext2, but under normal
> workloads it's not significant. The worst-case is 100 milliseconds,
> but that's when you're doing insane things to it.
>
> You may care to apply http://www.uow.edu.au/~andrewm/linux/2.4.1-pre10-low-latency.patch
> against 2.4.1-pre10 and see if it "feels" different. I'd be surprised
> if it does, but the result would be interresting.
>
> Note that the low-latency capability must be enabled under the
> "Processor type and features" menu, and if you also enable the
> low-latency sysctl option, you'll need to
>
> echo 1 > /proc/sys/kernel/lowlatency
>
> to make it happen. Creature feep :)
>
> Shawn Starr wrote:
> >
> > Sure, but Im not sure what to test ;)
> > If you've got any special patches for 2.4 lemme know and I'll apply them I've
> > got all night heh
> >
> > Shawn.
> >
> > Chris Mason wrote:
> >
> > > On Saturday, January 20, 2001 02:59:24 PM -0500 Gregory Maxwell
> > > <greg@linuxpower.cx> wrote:
> > >
> > > > On Sat, Jan 20, 2001 at 02:50:16PM -0500, Shawn Starr wrote:
> > > >> It just seems that since using 2.4 ive noticed my poor Pentium 200Mhz
> > > >> slow down whether being in X or otherwise. It just seems that the system
> > > >> is sluggish.
> > > >>
> > > >> I am using the new ReiserFS filesystem and I do know its still in heavy
> > > >> development perhaps my latency is due to this (?)
> > > >
> > > > Reiserfs uses much more complex data structures then ext2 (trees..). I
> > > > don't think that latency has ever been a design criteria and all of the
> > > > benchmarks they use are pretty much pure throughput tests.
> > > >
> > > > So it wouldn't be really surprising if reiserfs had very bad latency. You
> > > > should apply the timepegs patch and profile your kernel latency to see
> > > > where it's coming from.
> > >
> > > I'm actually very interested in fixing any latency problems. If you do
> > > these tests, please send the results along.
> > >
> > > -chris
> > > -
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