[PATCH V5 5/6] perf, x86: drain PEBS buffer during context switch

[Kan Liang]

From: Yan, Zheng <zheng.z.yan@xxxxxxxxx>

Flush the PEBS buffer during context switch if PEBS interrupt threshold
is larger than one. This allows perf to supply TID for sample outputs.

Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event.h           |  3 +++
 arch/x86/kernel/cpu/perf_event_intel.c     | 11 +++++++++-
 arch/x86/kernel/cpu/perf_event_intel_ds.c  | 33 ++++++++++++++++++++++++++++--
 arch/x86/kernel/cpu/perf_event_intel_lbr.c |  3 ---
 4 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index bc4ae3b..b4f6431 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -151,6 +151,7 @@ struct cpu_hw_events {
 	 */
 	struct debug_store	*ds;
 	u64			pebs_enabled;
+	bool			pebs_sched_cb_enabled;
 
 	/*
 	 * Intel LBR bits
@@ -739,6 +740,8 @@ void intel_pmu_pebs_enable_all(void);
 
 void intel_pmu_pebs_disable_all(void);
 
+void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in);
+
 void intel_ds_init(void);
 
 void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in);
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 9f1dd18..bdb2ffd 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2030,6 +2030,15 @@ static void intel_pmu_cpu_dying(int cpu)
 	fini_debug_store_on_cpu(cpu);
 }
 
+static void intel_pmu_sched_task(struct perf_event_context *ctx,
+				 bool sched_in)
+{
+	if (x86_pmu.pebs_active)
+		intel_pmu_pebs_sched_task(ctx, sched_in);
+	if (x86_pmu.lbr_nr)
+		intel_pmu_lbr_sched_task(ctx, sched_in);
+}
+
 PMU_FORMAT_ATTR(offcore_rsp, "config1:0-63");
 
 PMU_FORMAT_ATTR(ldlat, "config1:0-15");
@@ -2081,7 +2090,7 @@ static __initconst const struct x86_pmu intel_pmu = {
 	.cpu_starting		= intel_pmu_cpu_starting,
 	.cpu_dying		= intel_pmu_cpu_dying,
 	.guest_get_msrs		= intel_guest_get_msrs,
-	.sched_task		= intel_pmu_lbr_sched_task,
+	.sched_task		= intel_pmu_sched_task,
 };
 
 static __init void intel_clovertown_quirk(void)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index cf74a52..b8d0451 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -664,6 +664,19 @@ struct event_constraint *intel_pebs_constraints(struct perf_event *event)
 	return &emptyconstraint;
 }
 
+static inline void intel_pmu_drain_pebs_buffer(void)
+{
+	struct pt_regs regs;
+
+	x86_pmu.drain_pebs(&regs);
+}
+
+void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in)
+{
+	if (!sched_in)
+		intel_pmu_drain_pebs_buffer();
+}
+
 /*
  * Flags PEBS can handle without an PMI.
  *
@@ -704,13 +717,20 @@ void intel_pmu_pebs_enable(struct perf_event *event)
 	 * When the event is constrained enough we can use a larger
 	 * threshold and run the event with less frequent PMI.
 	 */
-	if (0 && /* disable this temporarily */
-	    (hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) &&
+	if ((hwc->flags & PERF_X86_EVENT_AUTO_RELOAD) &&
 	    !(event->attr.sample_type & ~PEBS_FREERUNNING_FLAGS)) {
 		threshold = ds->pebs_absolute_maximum -
 			x86_pmu.max_pebs_events * x86_pmu.pebs_record_size;
+		if (first_pebs) {
+			perf_sched_cb_inc(event->ctx->pmu);
+			cpuc->pebs_sched_cb_enabled = true;
+		}
 	} else {
 		threshold = ds->pebs_buffer_base + x86_pmu.pebs_record_size;
+		if (cpuc->pebs_sched_cb_enabled) {
+			perf_sched_cb_dec(event->ctx->pmu);
+			cpuc->pebs_sched_cb_enabled = false;
+		}
 	}
 	if (first_pebs || ds->pebs_interrupt_threshold > threshold)
 		ds->pebs_interrupt_threshold = threshold;
@@ -726,8 +746,17 @@ void intel_pmu_pebs_disable(struct perf_event *event)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct hw_perf_event *hwc = &event->hw;
+	struct debug_store *ds = cpuc->ds;
+
+	if (ds->pebs_interrupt_threshold >
+	    ds->pebs_buffer_base + x86_pmu.pebs_record_size)
+		intel_pmu_drain_pebs_buffer();
 
 	cpuc->pebs_enabled &= ~(1ULL << hwc->idx);
+	if (cpuc->pebs_sched_cb_enabled && !pebs_is_enabled(cpuc)) {
+		perf_sched_cb_dec(event->ctx->pmu);
+		cpuc->pebs_sched_cb_enabled = false;
+	}
 
 	if (event->hw.constraint->flags & PERF_X86_EVENT_PEBS_LDLAT)
 		cpuc->pebs_enabled &= ~(1ULL << (hwc->idx + 32));
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 0473874..1edd3b9 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -256,9 +256,6 @@ void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in)
 	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 LBR callstack feature is enabled and the stack was saved when
 	 * the task was scheduled out, restore the stack. Otherwise flush
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/