From: "Yan, Zheng" <zheng.z.yan@intel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, eranian@google.com, ak@linux.intel.com
Subject: Re: [PATCH 1/6] perf, x86: Basic Haswell LBR call stack support
Date: Tue, 23 Oct 2012 13:28:07 +0800 [thread overview]
Message-ID: <50862AE7.7080901@intel.com> (raw)
In-Reply-To: <1350902016.2768.85.camel@twins>
On 10/22/2012 06:33 PM, 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()?
>
So far we use the call stack feature only for ring 3. but even for ring 0,
it's OK. because LBR is disabled at the very beginning of PMI hander, and
enabled when exiting the PMI hander. the depth to _intel_pmu_lbr_enable/
_intel_pmu_lbr_disable are the same. So entries that are added by calling
_intel_pmu_lbr_disable will be popped during enabling LBR.
Regards
Yan, Zheng
next prev parent reply other threads:[~2012-10-23 5:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-22 6:11 [PATCH 0/6] perf, x86: Haswell LBR call stack support Yan, Zheng
2012-10-22 6:11 ` [PATCH 1/6] perf, x86: Basic " Yan, Zheng
2012-10-22 10:33 ` Peter Zijlstra
2012-10-22 11:23 ` Stephane Eranian
2012-10-23 5:31 ` Yan, Zheng
2012-10-22 13:45 ` Andi Kleen
2012-10-23 5:28 ` Yan, Zheng [this message]
2012-10-22 10:35 ` Peter Zijlstra
2012-10-22 13:49 ` Andi Kleen
2012-10-23 5:41 ` Yan, Zheng
2012-10-23 10:11 ` Peter Zijlstra
2012-10-23 12:09 ` Stephane Eranian
2012-10-23 16:34 ` Andi Kleen
2012-10-22 6:11 ` [PATCH 2/6] perf, x86: Introduce x86 special perf event context Yan, Zheng
2012-10-22 6:11 ` [PATCH 3/6] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2012-10-22 6:11 ` [PATCH 4/6] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2012-10-22 6:11 ` [PATCH 5/6] perf, x86: Use LBR call stack to get user callchain Yan, Zheng
2012-10-22 6:11 ` [PATCH 6/6] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
-- strict thread matches above, loose matches on Subject: below --
2012-10-22 5:57 [PATCH 0/6] perf, x86: Haswell LBR call stack support Yan, Zheng
2012-10-22 5:57 ` [PATCH 1/6] perf, x86: Basic " Yan, Zheng
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