Messages in this thread | | | Date | Sat, 23 Apr 2011 19:15:52 -0700 | From | Andi Kleen <> | Subject | Re: [generalized cache events] Re: [PATCH 1/1] perf tools: Add missing user space support for config1/config2 |
| |
> > That is what Andi is referring to. The issue causes bias and thus impacts > the quality of the samples. On SNB, there is a new INST_RETIRED:PREC_DIST > event. PREC_DIST=precise distribution. It tries to correct for the skid > on this event on INST_RETIRED with PEBS (look at Vol3b).
Unfortunately even PDIST doesn't completely fix the problem, but it only makes it somewhat better. Also it's only statistical, so you won't get a guaranteed answer for every sample.
-Andi
| |