Re: page fault fastpath: Increasing SMP scalability by introducingpte
From: Manfred Spraul
Date: Mon Aug 16 2004 - 00:21:53 EST
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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