From: Peter Zijlstra <peterz@infradead.org>
To: kan.liang@intel.com
Cc: eranian@google.com, linux-kernel@vger.kernel.org,
mingo@redhat.com, paulus@samba.org, acme@kernel.org,
ak@linux.intel.com, "Yan, Zheng" <zheng.z.yan@intel.com>
Subject: Re: [PATCH V5 08/16] perf, x86: track number of events that use LBR callstack
Date: Wed, 24 Sep 2014 14:53:49 +0200 [thread overview]
Message-ID: <20140924125349.GB2805@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <1410358153-421-9-git-send-email-kan.liang@intel.com>
On Wed, Sep 10, 2014 at 10:09:05AM -0400, kan.liang@intel.com wrote:
> @@ -204,9 +204,15 @@ void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in)
> }
> }
>
> +static inline bool branch_user_callstack(unsigned br_sel)
> +{
> + return (br_sel & X86_BR_USER) && (br_sel & X86_BR_CALL_STACK);
> +}
> +
> void intel_pmu_lbr_enable(struct perf_event *event)
> {
> struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
> + struct x86_perf_task_context *task_ctx;
>
> if (!x86_pmu.lbr_nr)
> return;
> @@ -220,6 +226,10 @@ void intel_pmu_lbr_enable(struct perf_event *event)
> }
> cpuc->br_sel = event->hw.branch_reg.reg;
>
> + task_ctx = event->ctx ? event->ctx->task_ctx_data : NULL;
> + if (task_ctx && branch_user_callstack(cpuc->br_sel))
> + task_ctx->lbr_callstack_users++;
> +
Does it make sense to flip those conditions to avoid a potentially
useless dereference?
next prev parent reply other threads:[~2014-09-24 12:53 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-10 14:08 [PATCH V5 00/16] perf, x86: Haswell LBR call stack support kan.liang
2014-09-10 14:08 ` [PATCH V5 01/16] perf, x86: Reduce lbr_sel_map size kan.liang
2014-09-24 10:50 ` Peter Zijlstra
2014-09-10 14:08 ` [PATCH V5 02/16] perf, core: introduce pmu context switch callback kan.liang
2014-09-24 11:23 ` Peter Zijlstra
2014-09-24 13:13 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 03/16] perf, x86: use context switch callback to flush LBR stack kan.liang
2014-09-10 14:09 ` [PATCH V5 04/16] perf, x86: Basic Haswell LBR call stack support kan.liang
2014-09-10 14:09 ` [PATCH V5 05/16] perf, core: pmu specific data for perf task context kan.liang
2014-09-10 14:09 ` [PATCH V5 06/16] perf, core: always switch pmu specific data during context switch kan.liang
2014-09-10 14:09 ` [PATCH V5 07/16] perf, x86: allocate space for storing LBR stack kan.liang
2014-09-10 14:09 ` [PATCH V5 08/16] perf, x86: track number of events that use LBR callstack kan.liang
2014-09-24 12:53 ` Peter Zijlstra [this message]
2014-10-07 2:59 ` Liang, Kan
2014-10-07 15:19 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 09/16] perf, x86: Save/resotre LBR stack during context switch kan.liang
2014-09-24 13:33 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 10/16] perf, core: simplify need branch stack check kan.liang
2014-09-24 13:55 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 11/16] perf, core: Pass perf_sample_data to perf_callchain() kan.liang
2014-09-24 14:15 ` Peter Zijlstra
2014-10-07 3:00 ` Liang, Kan
2014-10-07 15:24 ` Peter Zijlstra
2014-10-07 15:50 ` Liang, Kan
2014-10-07 16:29 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 12/16] perf, x86: use LBR call stack to get user callchain kan.liang
2014-09-10 14:09 ` [PATCH V5 13/16] perf, x86: re-organize code that implicitly enables LBR/PEBS kan.liang
2014-09-10 14:09 ` [PATCH V5 14/16] perf, x86: enable LBR callstack when recording callchain kan.liang
2014-09-24 14:21 ` Peter Zijlstra
2014-10-07 3:00 ` Liang, Kan
2014-10-07 15:25 ` Peter Zijlstra
2014-10-07 16:04 ` Liang, Kan
2014-09-10 14:09 ` [PATCH V5 15/16] perf, x86: disable FREEZE_LBRS_ON_PMI when LBR operates in callstack mode kan.liang
2014-09-10 14:09 ` [PATCH V5 16/16] perf, x86: Discard zero length call entries in LBR call stack kan.liang
-- strict thread matches above, loose matches on Subject: below --
2014-07-07 6:28 [PATCH v5 00/16] perf, x86: Haswell LBR call stack support Yan, Zheng
2014-07-07 6:28 ` [PATCH v5 08/16] perf, x86: track number of events that use LBR callstack Yan, Zheng
2001-01-08 2:29 [PATCH V5 00/16] perf, x86: Haswell LBR call stack support kan.liang
2001-01-08 2:29 ` [PATCH V5 08/16] perf, x86: track number of events that use LBR callstack kan.liang
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