lkml.org 
[lkml]   [2005]   [Oct]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: The "best" value of HZ
Date
On Fri, 28 Oct 2005 02:00 pm, Jesper Juhl wrote:
> On 10/28/05, Lee Revell <rlrevell@joe-job.com> wrote:
> > On Fri, 2005-10-28 at 03:31 +0100, Alistair John Strachan wrote:
> > > On Friday 28 October 2005 00:18, Claudio Scordino wrote:
> > > > Hi,
> > > >
> > > > during the last years there has been a lot of discussion about
> > > > the "best" value of HZ... On i386 was 100, then became 1000, and
> > > > finally was set to 250. I'm thinking to do an evaluation of this
> > > > parameter using different architectures.
> > > >
> > > > Has anybody thought to give the possibility to modify the value of HZ
> > > > at boot time instead of at compile time ? This would allow to easily
> > > > test different values on different machines and create a table
> > > > containing the "best" value for each architecture... At this moment,
> > > > instead, we have to recompile the kernel for each different value :(
> > > >
> > > > Do you think there would be much work to do that ?
> > > > Do you think it would be a desired feature the knowledge of the best
> > > > value for each architecture with more precision ?
> > >
> > > Google for "dynticks". There's obviously an overhead associated with HZ
> > > not being a constant (the compiler cannot optimise many expressions),
> > > but the feature is being worked on nonetheless.
> >
> > Well Linus had the best idea in that thread (as usual) which was to
> > implement "dynamic ticks" by leaving HZ a constant, setting it to a high
> > value, and skipping ticks when idle. Has there been any work in that
> > direction?
>
> i did a bit of work in that area, but the stuff I came up with never
> seemed to work right, so I dropped it.

It's all still in development at the moment but not far from being available
again. We stood back a bit to make some structural changes before trying to
make it ready for prime time.

Cheers,
Con
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-10-28 06:35    [from the cache]
©2003-2011 Jasper Spaans