From: Kan Liang <kan.liang@intel.com>
To: a.p.zijlstra@chello.nl, eranian@google.com
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, paulus@samba.org,
acme@kernel.org, jolsa@redhat.com, ak@linux.intel.com,
Kan Liang <kan.liang@intel.com>,
"Yan, Zheng" <zheng.z.yan@intel.com>
Subject: [PATCH V6 14/17] perf, x86: disable FREEZE_LBRS_ON_PMI when LBR operates in callstack mode
Date: Sun, 19 Oct 2014 17:55:09 -0400 [thread overview]
Message-ID: <1413755712-8259-15-git-send-email-kan.liang@intel.com> (raw)
In-Reply-To: <1413755712-8259-1-git-send-email-kan.liang@intel.com>
LBR callstack is designed for PEBS, It does not work well with
FREEZE_LBRS_ON_PMI for non PEBS event. If FREEZE_LBRS_ON_PMI is set for
non PEBS event, PMIs near call/return instructions may cause superfluous
increase/decrease of LBR_TOS.
This patch modifies __intel_pmu_lbr_enable() to not enable
FREEZE_LBRS_ON_PMI when LBR operates in callstack mode. We currently
don't use LBR callstack to capture kernel space callchain, so disabling
FREEZE_LBRS_ON_PMI should not be a problem.
Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 6e473c9..cd4bd6f 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -131,14 +131,23 @@ static void intel_pmu_lbr_filter(struct cpu_hw_events *cpuc);
static void __intel_pmu_lbr_enable(void)
{
- u64 debugctl;
struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
+ u64 debugctl, lbr_select = 0;
- if (cpuc->lbr_sel)
- wrmsrl(MSR_LBR_SELECT, cpuc->lbr_sel->config);
+ if (cpuc->lbr_sel) {
+ lbr_select = cpuc->lbr_sel->config;
+ wrmsrl(MSR_LBR_SELECT, lbr_select);
+ }
rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
- debugctl |= (DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
+ debugctl |= DEBUGCTLMSR_LBR;
+ /*
+ * LBR callstack does not work well with FREEZE_LBRS_ON_PMI.
+ * If FREEZE_LBRS_ON_PMI is set, PMI near call/return instructions
+ * may cause superfluous increase/decrease of LBR_TOS.
+ */
+ if (!(lbr_select & LBR_CALL_STACK))
+ debugctl |= DEBUGCTLMSR_FREEZE_LBRS_ON_PMI;
wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}
--
1.8.3.2
next prev parent reply other threads:[~2014-10-19 22:07 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-19 21:54 [PATCH V6 00/17] perf, x86: Haswell LBR call stack support Kan Liang
2014-10-19 21:54 ` [PATCH V6 01/17] perf, x86: Reduce lbr_sel_map size Kan Liang
2014-10-24 9:39 ` Peter Zijlstra
2014-11-04 1:07 ` Liang, Kan
2014-11-04 7:14 ` Peter Zijlstra
2014-11-04 7:16 ` Peter Zijlstra
2014-10-19 21:54 ` [PATCH V6 02/17] perf, core: introduce pmu context switch callback Kan Liang
2014-10-19 21:54 ` [PATCH V6 03/17] perf, x86: use context switch callback to flush LBR stack Kan Liang
2014-10-19 21:54 ` [PATCH V6 04/17] perf, x86: Basic Haswell LBR call stack support Kan Liang
2014-10-19 21:55 ` [PATCH V6 05/17] perf, core: pmu specific data for perf task context Kan Liang
2014-10-19 21:55 ` [PATCH V6 06/17] perf, core: always switch pmu specific data during context switch Kan Liang
2014-10-19 21:55 ` [PATCH V6 07/17] perf, x86: allocate space for storing LBR stack Kan Liang
2014-10-19 21:55 ` [PATCH V6 08/17] perf, x86: track number of events that use LBR callstack Kan Liang
2014-10-19 21:55 ` [PATCH V6 09/17] perf, x86: Save/resotre LBR stack during context switch Kan Liang
2014-10-19 21:55 ` [PATCH V6 10/17] perf, core: simplify need branch stack check Kan Liang
2014-10-19 21:55 ` [PATCH V6 11/17] perf, core: expose LBR call stack to user perf tool Kan Liang
2014-10-19 21:55 ` [PATCH V6 12/17] perf, x86: re-organize code that implicitly enables LBR/PEBS Kan Liang
2014-10-19 21:55 ` [PATCH V6 13/17] perf, x86: enable LBR callstack when recording callchain Kan Liang
2014-10-24 13:39 ` Jiri Olsa
2014-10-24 14:49 ` Liang, Kan
2014-10-19 21:55 ` Kan Liang [this message]
2014-10-19 21:55 ` [PATCH V6 15/17] perf, x86: Discard zero length call entries in LBR call stack Kan Liang
2014-10-19 21:55 ` [PATCH V6 16/17] perf tools: handle LBR call stack data Kan Liang
2014-10-19 21:55 ` [PATCH V6 17/17] perf tools: choose to dump callchain from LBR and FP Kan Liang
2014-10-24 13:36 ` Jiri Olsa
2014-10-24 13:55 ` Jiri Olsa
2014-10-24 15:20 ` Liang, Kan
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