On Tue, Sep 10, 2013 at 5:28 PM, Peter Zijlstra <pet...@infradead.org> wrote: > 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. > I agree with you.
I am curious to see what's in those entries. If they are all zeroes, then we know only the pointer is bogus. Let me add some instrumentation to check that. >> 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. I agree. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
