Re: [patch] i386 dynamic ticks 2.6.13-rc4 (code reordered)

Tony Lindgren
2005-08-02T11:32:12Z

* Con Kolivas <kernel@kolivas.org> [050802 03:54]:
> On Tue, 2 Aug 2005 18:15, Tony Lindgren wrote:
> > * Con Kolivas <kernel@kolivas.org> [050802 00:36]:
> > > On Tue, 2 Aug 2005 05:17 pm, Tony Lindgren wrote:
> > > > But this you can verify by booting to single user mode and then running
> > > > pmstats 5, and if ticks is not below 25HZ, there's something in the
> > > > kernel polling.
> > >
> > > I'm removing modules and they don't seem to do anything so I'm not sure
> > > what else to try.
> >
> > If you have 130HZ in single user mode, it's some kernel driver.
> > You could printk the the next timer, then grep for that in System.map:
>
> I kept pulling modules and eventually got to 27Hz so something was definitely
> happening.

Cool.

> I need to ask you why you think limiting the maximum Hz is a bad idea? On a
> laptop, say we have set the powersave governor, we have already told the
> kernel we are interested in maximising power saving at the expense of
> performance. Would it not be appropriate for this to be linked in a way that
> sets maximum Hz to some value that maximises power save (whatever that value
> is) at that time?

With dyntick the system will run at max HZ only when busy. It is possible
that cutting down max HZ might cause some savings while busy, but I would
assume the savings are minimal.

I personally prefer to have the performance available when needed, and
max savings while idle.

Tony