Re: [PATCH] rwsem: reduce spinlock contention in wakeup code path

[Waiman Long]

On 10/01/2013 03:33 AM, Ingo Molnar wrote:
> * Waiman Long<waiman.long@xxxxxx>  wrote:
>
> > > I think Waiman's patches (even the later ones) made the queued rwlocks
> > > be a side-by-side implementation with the old rwlocks, and I think
> > > that was just being unnecessarily careful. It might be useful for
> > > testing to have a config option to switch between the two, but we
> > > might as well go all the way.
> > It is not actually a side-by-side implementation. A user can choose
> > either regular rwlock or the queue one, but never both by setting a
> > configuration parameter. However, I now think that maybe we should do it
> > the lockref way by pre-determining it on a per-architecture level
> > without user visible configuration option.
> Well, as I pointed it out to you during review, such a Kconfig driven
> locking API choice is a no-go!
>
> What I suggested instead: there's absolutely no problem with providing a
> better rwlock_t implementation, backed with numbers and all that.
>
> Thanks,
>
> 	Ingo

Yes, this is what I am planning to do. The next version of my qrwlock 
patch will force the switch to queue rwlock for x86 architecture. The 
other architectures have to be done separately.

-Longman

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