On Fri, Nov 10, 2017 at 09:05:20AM +0100, Peter Zijlstra wrote:
> On Fri, Nov 10, 2017 at 03:10:17PM +0800, Peter Xu wrote:
> > I came to this when reading kvm_vcpu_wake_up(), so that only affects
> > some statistic which may not be that critical. However I don't know
> > whether there would be any other real use case that we would like to
> > know exactly whether a call to [s]wake_up() has really done something
> > or just returned with a NOP.
> >
> > Anyway, please let me know if you think the same change to wake_up()
> > would be meaningful, otherwise I can drop this patch and post another
> > KVM-only one to clean up the redundant callers of swait_active(),
> > since even if we dropped that list check in 35a2897c2a30, we'll do
> > that again in swake_up_locked().
>
> See commits:
>
> 8cd641e3c7cb ("sched/wait: Add swq_has_sleeper()")
> 5e0018b3e39e ("kvm: Serialize wq active checks in kvm_vcpu_wake_up()")
>
>
> In any case, I don't think we want the change you propose. The numbers
> don't mean much and there's no point in making all the callers in the
> kernel slower for it.
I see. And also we can introduce a new API for that if really needed.
I'll repost with KVM only changes. Thanks for reviewing.
--
Peter Xu
