On Tue, 2014-05-06 at 12:29 +0200, Peter Zijlstra wrote: > So you forgot to CC Linus, Linus has expressed some dislike for > preemptible mmu_notifiers in the recent past: > > https://lkml.org/lkml/2013/9/30/385 I'm glad this came up again. So I've been running benchmarks (mostly aim7, which nicely exercises our locks) comparing my recent v4 for rwsem optimistic spinning against previous implementation ideas for the anon-vma lock, mostly: - rwsem (currently) - rwlock_t - qrwlock_t - rwsem+optspin Of course, *any* change provides significant improvement in throughput for several workloads, by avoiding to block -- there are more performance numbers in the different patches. This is fairly obvious. What is perhaps not so obvious is that rwsem+optimistic spinning beats all others, including the improved qrwlock from Waiman and Peter. This is mostly because of the idea of cancelable MCS, which was mimic'ed from mutexes. The delta in most cases is around +10-15%, which is non trivial. I mention this because from a performance PoV, we'll stop caring so much about the type of lock we require in the notifier related code. So while this is not conclusive, I'm not as opposed to keeping the locks blocking as I once was. Now this might still imply things like poor design choices, but that's neither here nor there. /me sees Sagi smiling ;) Thanks, Davidlohr -- 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>