On Wed, 2010-02-03 at 15:07 +0100, Stephane Eranian wrote: > >> The only improvement that PEBS provides is that you get an IP and the > >> machine state at retirement of an instruction that caused the event to > >> increment. Thus, the IP points to the next dynamic instruction. The > >> instruction > >> is not the one that cause the P-th occurence of the event, if you set the > >> period to P. It is at P+N, where N cannot be predicted and varies depending > >> on the event and executed code. This introduces some bias in the samples.. > > > > I'm not sure I follow, it records the next event after overflow, doesn't > > that make it P+1? > > > That is not what I wrote. I did not say if records at P+1. I said it records > at P+N, where N varies from sample to sample and cannot be predicted. > N is expressed in the unit of the sampling event.
OK, so I'm confused. The manual says it arms the PEBS assist on overflow, and the PEBS thing will then record the next event. Which to me reads like P+1. You're saying they're wrong and they record a random event after the overflow? ------------------------------------------------------------------------------ The Planet: dedicated and managed hosting, cloud storage, colocation Stay online with enterprise data centers and the best network in the business Choose flexible plans and management services without long-term contracts Personal 24x7 support from experience hosting pros just a phone call away. http://p.sf.net/sfu/theplanet-com _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
