Messages in this thread | | | Date | Tue, 10 Sep 2013 17:28:45 +0200 | From | Peter Zijlstra <> | Subject | Re: PEBS bug on HSW: "Unexpected number of pebs records 10" (was: Re: [GIT PULL] perf changes for v3.12) |
| |
On Tue, Sep 10, 2013 at 07:15:19AM -0700, Stephane Eranian wrote: > The threshold is where to generate the interrupt. It does not mean > where to stop PEBS recording.
It does, since we don't set a reset value. So once a PEBS assist happens, that counter stops until we reprogram it in the PMI.
> So it is possible that in HSW, we may > get into a situation where it takes time to get to the handler to stop > the PMU. I don't know how given we use NMI. Well, unless we were > already servicing an NMI at the time. But given that we stop the PMU > almost immediately in the handler, I don't see how that would > possible. The other oddity in HSW is that we clear the NMI on entry > to the handler and not at the end. I never gotten an good explanation > as to why that was necessary. So maybe it is related...
Even if the PMI was delayed that counter would never do another entry. So I really don't see how we can have more than nr_counters PEBS entries in the buffer.
| |