Re: [PATCH -tip-rcu] Make rcutorture more vicious: make quiescent rcutorture less power-hungry

Arjan van de Ven
2008-06-23T20:07:57Z

On Mon, 23 Jun 2008 20:02:54 +0000
Darren Hart <dvhltc@us.ibm.com> wrote:

> On Mon, 2008-06-23 at 11:07 -0700, Arjan van de Ven wrote:
> > On Mon, 23 Jun 2008 17:54:09 +0000
> > Darren Hart <dvhltc@us.ibm.com> wrote:
> >
> > > I'm a little concerned about how this will affect real-time
> > > performance, as queueing up lots of timers all at once can lead to
> > > long running timer expiration handlers. If just a
> > > schedule_timeout, I suppose we are only looking at a process
> > > wakeup, as opposed to a softirq context callback function?
> >
> > in reality, the time it takes to deliver the interrupt (including
> > waking the CPU up etc), is likely to be an order or two of magnitude
> > higher than this kind of code loop....
>
> Sure, if we just look at one of them. Any idea how many such items
> we're looking at rounding up to fire at the same time? Is it dozens,
> hundreds, thousands?
>

so far, in practice, it's still single-digit amounts.

There's not that many timers that run normally.
(based on powertop data from many systems)

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