* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Sat, Dec 1, 2012 at 4:26 AM, Ingo Molnar <mingo@xxxxxxxxxx> 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. Yeah. > 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. I'll try the rwsem and see how it goes? > 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. Hm, indeed. For performance runs I typically disable lock debugging - which might have made me not directly notice some of the performance problems. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>