Christoph Lameter wrote:
The page fault handler attempts to use the page_table_lock only for short
time periods. It repeatedly drops and reacquires the lock. When the lock
is reacquired, checks are made if the underlying pte has changed before
replacing the pte value. These locations are a good fit for the use of
ptep_cmpxchg.
The following patch allows to remove the first time the page_table_lock is
acquired and uses atomic operations on the page table instead. A section
using atomic pte operations is begun with
page_table_atomic_start(struct mm_struct *)
and ends with
page_table_atomic_stop(struct mm_struct *)
Hmm, this is moving toward the direction my patches take.
I think it may be the right way to go if you're lifting the ptl
from some core things, because some architectures won't want to
audit and stuff, and some may need the lock.
Naturally I prefer the complete replacement that is made with
my patch - however this of course means one has to move
*everything* over to be pte_cmpxchg safe, which runs against
your goal of getting the low hanging fruit with as little fuss
as possible for the moment.
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