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

[Arjan van de Ven]

On Mon, 23 Jun 2008 20:02:54 +0000
Darren Hart <dvhltc@xxxxxxxxxx> 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@xxxxxxxxxx> 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)

-- 
If you want to reach me at my work email, use arjan@xxxxxxxxxxxxxxx
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/