Re: [RFC PATCH v2 3/5] futex: Throughput-optimized (TO) futexes

[Waiman Long]

On 09/22/2016 05:41 PM, Thomas Gleixner wrote:
> On Thu, 22 Sep 2016, Davidlohr Bueso wrote:
> > On Thu, 22 Sep 2016, Waiman Long wrote:
> >
> > > BTW, my initial attempt for the new futex was to use the same workflow as
> > > the PI futexes, but use mutex which has optimistic spinning instead of
> > > rt_mutex.
> > Btw, Thomas, do you still have any interest pursuing this for rtmutexes from
> > -rt into mainline? If so I can resend the patches from a while ago.
> Certainly yes. My faint memory tells me that there was some potential issue
> due to boosting the owner only if it gets scheduled out, but I might be
> wrong.

It is tricky to add optimistic spinning to rtmutexes because of the need 
to observe process priorities. It is certainly possible to make the top 
waiter spin, but then I am not sure how much performance gain with just 
that.

Cheers,
Longman