Re: page fault fastpath: Increasing SMP scalability by introducingpte

[Manfred Spraul]

Christoph Lameter wrote:

> On Sun, 15 Aug 2004, Manfred Spraul wrote:
>
>  
>
> > Very odd. Why do you see a problem with the page_table_lock but no
> > problem from the mmap semaphore?
> >    
>
> Because there is a only a down_read() call for the mmap semaphore before
> invoking handle_mm_fault. This is a rw semaphore which means that multiple
> processors/processes may be entering handle_mm_fault with a read lock on
> the mmap semaphore.
>  
As far as I can see the actual hold times on the page_table_lock are not 
that long and down_read() causes a cache line transfer, too.
But you have answered my question in your first mail: There are 2-5 
spin_lock calls per page fault but only one down_read call.

--
   Manfred
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