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

[Larry Woodman <lwoodman@redhat.com>]

Rik van Riel wrote:

>On Fri, 04 Jan 2008 17:34:00 +0100
>Andi Kleen <andi@firstfloor.org> wrote:
>  
>
>>Lee Schermerhorn <Lee.Schermerhorn@hp.com> 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.
>
>  
>