Re: [PATCH 1/1] perf/x86/intel: Add perf core PMU support for Intel Knights Landing
From: Harish Chegondi
Date: Wed Dec 09 2015 - 18:44:14 EST
On 12/09/2015 03:37 PM, Peter Zijlstra wrote:
> On Wed, Dec 09, 2015 at 03:22:29PM -0800, Harish Chegondi wrote:
>> On 12/08/2015 12:37 AM, Peter Zijlstra wrote:
>>> On Mon, Dec 07, 2015 at 02:28:18PM -0800, Harish Chegondi wrote:
>>>> Knights Landing core is based on Silvermont core with several differences.
>>>> Like Silvermont, Knights Landing has 8 pairs of LBR MSRs. However, the
>>>> LBR MSRs addresses match those of the Xeon cores' first 8 pairs of LBR MSRs
>>>> +/* Knights Landing */
>>>> +void intel_pmu_lbr_init_knl(void)
>>>> + x86_pmu.lbr_nr = 8;
>>>> + x86_pmu.lbr_tos = MSR_LBR_TOS;
>>>> + x86_pmu.lbr_from = MSR_LBR_NHM_FROM;
>>>> + x86_pmu.lbr_to = MSR_LBR_NHM_TO;
>>>> + x86_pmu.lbr_sel_mask = LBR_SEL_MASK;
>>>> + x86_pmu.lbr_sel_map = snb_lbr_sel_map;
>>> Also, unlike Silvermont, this thing seems to have hardware LBR filters.
>>> So would it not be more accurate to say the KNL has a big core LBR
>>> instead? (Note that this LBR setup isn't specific to Xeon's, all of the
>>> Core chips have this, including the client parts).
>> We cannot say that KNL has a big core LBR. This is because
>> architectural MSR IA32_PERF_CAPABILITIES[5:0] which indicates the
>> format of the address that is stored in the LBR stack is different for
>> KNL (IA32_PERF_CAPABILITIES[5:0] = 0x1) and big core (for example,
>> Haswell IA32_PERF_CAPABILITIES[5:0]=0x4). Haswell LBR stack has TSX
>> info which KNL LBR stack doesn't have.
> Fair enough I suppose. Applied the patch.
Thank you Peter!
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