Re: [bisected] pre-3.16 regression on open() scalability

From: Paul E. McKenney
Date: Wed Jun 18 2014 - 08:56:27 EST


On Wed, Jun 18, 2014 at 05:40:28AM -0700, Andi Kleen wrote:
> On Tue, Jun 17, 2014 at 09:47:45PM -0700, Paul E. McKenney wrote:
> > On Tue, Jun 17, 2014 at 07:27:31PM -0700, Andi Kleen wrote:
> > > > OK. What would you suggest instead? If all we do is to revert the
> > >
> > > Hang checker should have two timer phases:
> > >
> > > Timer fires first time:
> > > - Save context switch counter on that. Force a reschedule to some
> > > work queue. Rearm timer
> > >
> > > Timer fires again:
> > > - Check reschedule count. If the reschedule count changed
> > > it was a real hang, otherwise ignore.
> >
> > I could take that approach, but the RT guys aren't going to thank me for
> > the wakeup associated with the work queue. I suppose that I could use
>
> They can disable the hang timer if it's really problem.
>
> If they cannot tolerate a single context switch they likely
> cannot tolerate a timer firing either.

Ah, but I make the timer fire on some other CPU.

Thanx, Paul

--
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/