Re: [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq

Thomas Gleixner
2015-08-17T20:31:07Z

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On Fri, 7 Aug 2015, Peter Zijlstra wrote:
> On Fri, Aug 07, 2015 at 12:57:38PM +0200, Peter Zijlstra wrote:
>
> > > >+void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
>
> > > this one has no users the __ suggests that it is locked edition. Maybe
> > > it is for the completions…
> >
> > Yeah, who knows, I certainly do not anymore ;-)
>
> On that, we cannot convert completions to swait. Because swait wake_all
> must not happen from IRQ context, and complete_all() typically is used
> from just that.

Well, completions are not the ones which have a gazillion of waiters
and we got quite some performance back from using swait in completions
on RT.

Thanks,

tglx