Messages in this thread | | | Date | Tue, 23 Oct 2012 13:31:01 +0800 | From | "Yan, Zheng" <> | Subject | Re: [PATCH 1/6] perf, x86: Basic Haswell LBR call stack support |
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On 10/22/2012 07:23 PM, Stephane Eranian wrote: > On Mon, Oct 22, 2012 at 12:33 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: >> >> On Mon, 2012-10-22 at 14:11 +0800, Yan, Zheng wrote: >>> + /* LBR callstack does not work well with FREEZE_LBRS_ON_PMI */ >>> + if (!cpuc->lbr_sel || !(cpuc->lbr_sel->config & LBR_CALL_STACK)) >>> + debugctl |= DEBUGCTLMSR_FREEZE_LBRS_ON_PMI; >> > Is this a bug or a feature? > It's a hardware bug. If FREEZE_LBRS_ON_PMI is set, PMI may corrupt the call stack records.
Regards Yan, Zheng
>> >> How useful it is without this? How many calls between PMI and us getting >> to intel_pmu_lbr_read()? > > Agreed with Peter. Freeze on PMI is critical for LBR in general. >
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