On Fri, Nov 29, 2013 at 04:44:41PM +0000, Linus Torvalds wrote: > > On Nov 29, 2013 8:18 AM, "Will Deacon" > <will.deacon@xxxxxxx<mailto:will.deacon@xxxxxxx>> wrote: > > > > To get some sort of idea, I tried adding a dmb to the start of > > spin_unlock on ARMv7 and I saw a 3% performance hit in hackbench on my > > dual-cluster board. > > Don't do a dmb. Just do a dummy release. You just said that on arm64 a > unlock+lock is a memory barrier, so just make the mb__before_spinlock() be > a dummy store with release to the stack.. Good idea! That should work quite nicely (I don't have anything sane I can benchmark it on), so I think that solves the issue I was moaning about. Will -- 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>