Re: [patch 00/19] VM pageout scalability improvements

[Larry Woodman]

Rik van Riel wrote:

> On Fri, 04 Jan 2008 17:34:00 +0100
> Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>  
>
> > Lee Schermerhorn <Lee.Schermerhorn@xxxxxx> writes:
> >
> >    
> >
> > > We can easily [he says, glibly] reproduce the hang on the anon_vma lock
> > >      
> > Is that a NUMA platform? On non x86? Perhaps you just need queued spinlocks?
> >    
>
> I really think that the anon_vma and i_mmap_lock spinlock hangs are
> due to the lack of queued spinlocks.  Not because I have seen your
> system hang, but because I've seen one of Larry's test systems here
> hang in scary/amusing ways :)
Changing the anon_vma->lock into a rwlock_t helps because 
page_lock_anon_vma()
can take it for read and thats where the contention is.  However its the 
fact that under
some tests, most of the pages are in vmas queued to one anon_vma that 
causes so much
lock contention.


> With queued spinlocks the system should just slow down, not hang.
>
>  


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