Messages in this thread | | | Date | Mon, 22 Oct 2012 06:45:05 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH 1/6] perf, x86: Basic Haswell LBR call stack support |
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On Mon, Oct 22, 2012 at 12:33:36PM +0200, Peter Zijlstra 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; > > How useful it is without this? How many calls between PMI and us getting > to intel_pmu_lbr_read()?
We use it only for ring 3. For ring 0 we assume frame pointer or dwarf information.
So the CPL filter acts as the freeze.
-andi
-- ak@linux.intel.com -- Speaking for myself only
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