On Fri, Nov 29, 2013 at 08:44:41AM -0800, Linus Torvalds wrote: > On Nov 29, 2013 8:18 AM, "Will Deacon" <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.. > > That should be noticeably cheaper than a full dmb. Cute! I like it! ;-) Thanx, Paul -- 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>