lkml.org 
[lkml]   [2009]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: Regarding dm-ioband tests
From
Hi,

Fabio Checconi <fchecconi@gmail.com> wrote:
> Hi,
>
> > From: Rik van Riel <riel@redhat.com>
> > Date: Tue, Sep 08, 2009 03:24:08PM -0400
> >
> > Ryo Tsuruta wrote:
> > >Rik van Riel <riel@redhat.com> wrote:
> >
> > >>Are you saying that dm-ioband is purposely unfair,
> > >>until a certain load level is reached?
> > >
> > >Not unfair, dm-ioband(weight policy) is intentionally designed to
> > >use bandwidth efficiently, weight policy tries to give spare bandwidth
> > >of inactive groups to active groups.
> >
> > This sounds good, except that the lack of anticipation
> > means that a group with just one task doing reads will
> > be considered "inactive" in-between reads.
> >
>
> anticipation helps in achieving fairness, but CFQ currently disables
> idling for nonrot+NCQ media, to avoid the resulting throughput loss on
> some SSDs. Are we really sure that we want to introduce anticipation
> everywhere, not only to improve throughput on rotational media, but to
> achieve fairness too?

I'm also not sure if it's worth introducing anticipation everywhere.
The storage devices are becoming faster and smarter every year. In
practice, I did a benchmark with a SAN storage and the noop scheduler
got the best result.

However, I'll consider how IO from one task should take care of.

Thanks,
Ryo Tsuruta


\
 
 \ /
  Last update: 2009-09-09 11:27    [W:0.185 / U:0.096 seconds]
©2003-2011 Jasper Spaans. Advertise on this site