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

Paul E. McKenney
2008-06-23T20:25:39Z

On Mon, Jun 23, 2008 at 08:02:54PM +0000, Darren Hart 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?

Hello, Darren,

Wouldn't these timers be running at low priority, so that high-priority
realtime tasks would preempt them?

Thanx, Paul