On Fri, 2012-09-28 at 10:54 +0200, Stephane Eranian wrote: > On Fri, Sep 28, 2012 at 10:43 AM, Peter Zijlstra <a.p.zijls...@chello.nl> > wrote: > > On Thu, 2012-09-27 at 21:31 -0700, Andi Kleen wrote: > >> + if (event->attr.precise_ip > 1 && > >> x86_pmu.intel_cap.pebs_format < 2) { > > > > Shouldn't that be: && x86_pmu.intel_cap.pebs_trap, like most other sites > > instead? Or didn't they flip the trap capability on Haswell? > > On Haswell, you get the event_ip which points to the sampled > instruction, i.e., the off-by-one > error can be avoided by using that value instead of pebs.rip. The nice > side effect is that you > free the LBR and minimize the overhead (no fixups). Therfore the LBR > filter can have any > setting when combined with PEBS, thus we do not need to check for > compatibility nor force > any setting for the LBR filter.
Yes I got that, but what good is that trap capability flag if they don't use it? Them adding a second u64 to the format to report it seems to suggest their trap capability is pointless, but nowhere has this been explained. -- 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/