On Mon, Mar 03, 2014 at 07:58:19PM +0100, Andi Kleen wrote: > On Mon, Mar 03, 2014 at 07:41:17PM +0100, Peter Zijlstra wrote: > > On Mon, Mar 03, 2014 at 01:07:00PM -0500, Joe Mario wrote: > > > If you only sample on the HITMs then you don't get the store misses. > > > That means you'll not be able to detect who is simultaneously tugging > > > on the same cache lines. That gives up much of the value of "perf > > > c2c". > > > > As long as you know which lines are hurting bringing in (loads) you can > > often figure out who is doing the stores on them. > > Yes, especially since every store is a load too (unless you're talking > WC)
Thoughts on how to determine which load is a potential store? I agree every store needs to load the cacheline, but I wasn't sure if there was an approach that could be applied to determine anything useful. Cheers, Don > > The method c2c uses is more exact, but keep in mind it's a sampling > heuristic in any cases, with some potential bias. load-latency tags > the loads randomly and there's no guarantee that tagging is fully > uniform. Also you only see a subset in any case. > > > > > > As we developed this, we ended up settling on Ivy Bridge to get the > > > behavior we wanted. > > > > Wouldn't SNB also work? > > Yes. > > Haswell is best however because it can report addresses on far more > events. > > -Andi > > -- > [email protected] -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
