perf/x86/intel: Track number of events that use the LBR callstack

When enabling/disabling an event, check if the event uses the LBR
callstack feature, adjust the LBR callstack usage count accordingly.
Later patch will use the usage count to decide if LBR stack should
be saved/restored.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-9-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index ac8279e560a177923269d2d5f90889f82c604f88..ac8e54200934d6298a89fe43bd5212034ce1004b 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -205,9 +205,15 @@ 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 = this_cpu_ptr(&cpu_hw_events);
+       struct x86_perf_task_context *task_ctx;
 
        if (!x86_pmu.lbr_nr)
                return;
@@ -222,6 +228,12 @@ void intel_pmu_lbr_enable(struct perf_event *event)
        }
        cpuc->br_sel = event->hw.branch_reg.reg;
 
+       if (branch_user_callstack(cpuc->br_sel) && event->ctx &&
+                                       event->ctx->task_ctx_data) {
+               task_ctx = event->ctx->task_ctx_data;
+               task_ctx->lbr_callstack_users++;
+       }
+
        cpuc->lbr_users++;
        perf_sched_cb_inc(event->ctx->pmu);
 }
@@ -229,10 +241,17 @@ void intel_pmu_lbr_enable(struct perf_event *event)
 void intel_pmu_lbr_disable(struct perf_event *event)
 {
        struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+       struct x86_perf_task_context *task_ctx;
 
        if (!x86_pmu.lbr_nr)
                return;
 
+       if (branch_user_callstack(cpuc->br_sel) && event->ctx &&
+                                       event->ctx->task_ctx_data) {
+               task_ctx = event->ctx->task_ctx_data;
+               task_ctx->lbr_callstack_users--;
+       }
+
        cpuc->lbr_users--;
        WARN_ON_ONCE(cpuc->lbr_users < 0);
        perf_sched_cb_dec(event->ctx->pmu);