Re: [RFC PATCH 00/11] sched: CFS low-latency features

Mathieu Desnoyers
2010-08-27T15:50:17Z

* Thomas Gleixner (tglx@linutronix.de) wrote:
> On Thu, 26 Aug 2010, Mathieu Desnoyers wrote:
[...]
> > Hrm, thinking about it a little more, one of the "plus" sides of these
> > SIGEV_THREAD timers is that a single timer can fork threads that will run on
> > many cores on a multi-core system. If we go for preallocation of a single
> > thread, we lose that. Maybe we could think of a way to preallocate a thread pool
> > instead ?
>
> Why should a single timer fork many threads? Just because a previous
> thread did not complete before the timer fires again? That's
> braindamage as all threads call the same function which then needs to
> be serialized anyway. We really do not need a function which creates
> tons of threads which get all stuck on the same resource.

It could make sense if the workload is mostly CPU-bound and there is only a very
short critical section shared between the threads. But I agree that in many
cases this will generate an utter contention mess.

Thanks,

Mathieu

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.