Re: Performance regression from switching lock to rw-sem foranon-vma tree

[Tim Chen]

On Fri, 2013-06-14 at 15:47 -0700, Michel Lespinasse wrote:
> On Fri, Jun 14, 2013 at 3:31 PM, Davidlohr Bueso <davidlohr.bueso@xxxxxx> wrote:
> > A few ideas that come to mind are avoiding taking the ->wait_lock and
> > avoid dealing with waiters when doing the optimistic spinning (just like
> > mutexes do).
> >
> > I agree that we should first deal with the optimistic spinning before
> > adding the MCS complexity.
> 
> Maybe it would be worth disabling the MCS patch in mutex and comparing
> that to the rwsem patches ? Just to make sure the rwsem performance
> delta isn't related to that.
> 

I've tried to back out the MCS patch.  In fact, for exim, it is about 1%
faster without MCS.  So the better performance of mutex I saw was not
due to MCS.  Thanks for the suggestion.

Tim

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