On Thu, Jul 06, 2017 at 06:10:47PM +0200, Peter Zijlstra wrote: > On Thu, Jul 06, 2017 at 08:21:10AM -0700, Paul E. McKenney wrote: > > And yes, there are architecture-specific optimizations for an > > empty spin_lock()/spin_unlock() critical section, and the current > > arch_spin_unlock_wait() implementations show some of these optimizations. > > But I expect that performance benefits would need to be demonstrated at > > the system level. > > I do in fact contended there are any optimizations for the exact > lock+unlock semantics. You lost me on this one. > The current spin_unlock_wait() is weaker. Most notably it will not (with > exception of ARM64/PPC for other reasons) cause waits on other CPUs. Agreed, weaker semantics allow more optimizations. So use cases needing only the weaker semantics should more readily show performance benefits. But either way, we need compelling use cases, and I do not believe that any of the existing spin_unlock_wait() calls are compelling. Perhaps I am confused, but I am not seeing it for any of them. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
