>>> On 27.12.12 at 20:09, Rik van Riel <r...@redhat.com> wrote: > On 12/27/2012 01:41 PM, Jan Beulich wrote: >>>>> Rik van Riel <r...@redhat.com> 12/27/12 4:01 PM >>> >>> On 12/27/2012 09:27 AM, Eric Dumazet wrote: >>>> So the hash sounds good to me, because the hash key could mix both lock >>>> address and caller IP ( __builtin_return_address(1) in >>>> ticket_spin_lock_wait()) >>> >>> The lock acquisition time depends on the holder of the lock, >>> and what the CPUs ahead of us in line will do with the lock, >>> not on the caller IP of the spinner. >> >> The lock holder could supply its __builtin_return_address(0) for use >> in eventual hashing. >> >> Also, with all of this - did you evaluate the alternative of using >> monitor/mwait instead? > > How much bus traffic do monitor/mwait cause behind the scenes?
I would suppose that this just snoops the bus for writes, but the amount of bus traffic involved in this isn't explicitly documented. One downside of course is that unless a spin lock is made occupy exactly a cache line, false wakeups are possible. Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
