Messages in this thread | | | Date | Mon, 3 Mar 2014 19:58:19 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH 08/19] perf c2c: Shared data analyser |
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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)
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
-- ak@linux.intel.com -- Speaking for myself only.
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