Messages in this thread |  | | From | Linus Torvalds <> | Date | Sat, 1 Dec 2012 10:38:16 -0800 | Subject | Re: [RFC PATCH] mm/migration: Remove anon vma locking from try_to_unmap() use |
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On Sat, Dec 1, 2012 at 4:26 AM, Ingo Molnar <mingo@kernel.org> wrote: > > > So as a quick concept hack I wrote the patch attached below. > (It's not signed off, see the patch description text for the > reason.)
Well, it confirms that anon_vma locking is a big problem, but as outlined in my other email it's completely incorrect from an actual behavior standpoint.
Btw, I think the anon_vma lock could be made a spinlock instead of a mutex or rwsem, but that would probably take more work. We *shouldn't* be doing anything that needs IO inside the anon_vma lock, though, so it *should* be doable. But there are probably quite a bit of allocations inside the lock, and I know it covers huge areas, so a spinlock might not only be hard to convert to, it quite likely has latency issues too.
Oh, btw, MUTEX_SPIN_ON_OWNER may well improve performance too, but it gets disabled by DEBUG_MUTEXES. So some of the performance impact of the vma locking may be *very* kernel-config dependent.
Linus
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