linux-kernel - [RFC][PATCH] perf, pebs: Add PEBS v3 record decoding

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Date:	Tue, 12 May 2015 15:25:57 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Kan Liang <kan.liang@...el.com>
Cc:	mingo@...nel.org, acme@...radead.org, eranian@...gle.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] perf, pebs: Add PEBS v3 record decoding



So seeing how I have both this series and Andi's SKL patches, I did the
below on top of them both.

Could someone try that?

---
Subject: perf, pebs: Add PEBS v3 record decoding
From: Peter Zijlstra <peterz@...radead.org>
Date: Tue May 12 15:18:18 CEST 2015

PEBS v3 as present on Skylake fixed the long standing issue of the
status bits. They now really reflect the events that generated the
record.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kernel/cpu/perf_event_intel_ds.c |   30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -1034,6 +1034,9 @@ get_next_pebs_record_by_bit(void *base,
 		struct pebs_record_nhm *p = at;
 
 		if (test_bit(bit, (unsigned long *)&p->status)) {
+			/* PEBS v3 has accurate status bits */
+			if (x86_pmu.intel_cap.pebs_format >= 3)
+				return at;
 
 			if (p->status == (1 << bit))
 				return at;
@@ -1055,20 +1058,18 @@ static void __intel_pmu_pebs_event(struc
 {
 	struct perf_sample_data data;
 	struct pt_regs regs;
-	int i;
 	void *at = get_next_pebs_record_by_bit(base, top, bit);
 
 	if (!intel_pmu_save_and_restart(event) &&
 	    !(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD))
 		return;
 
-	if (count > 1) {
-		for (i = 0; i < count - 1; i++) {
-			setup_pebs_sample_data(event, iregs, at, &data, &regs);
-			perf_event_output(event, &data, &regs);
-			at += x86_pmu.pebs_record_size;
-			at = get_next_pebs_record_by_bit(at, top, bit);
-		}
+	while (count > 1) {
+		setup_pebs_sample_data(event, iregs, at, &data, &regs);
+		perf_event_output(event, &data, &regs);
+		at += x86_pmu.pebs_record_size;
+		at = get_next_pebs_record_by_bit(at, top, bit);
+		count--;
 	}
 
 	setup_pebs_sample_data(event, iregs, at, &data, &regs);
@@ -1124,9 +1125,9 @@ static void intel_pmu_drain_pebs_nhm(str
 	struct debug_store *ds = cpuc->ds;
 	struct perf_event *event;
 	void *base, *at, *top;
-	int bit;
 	short counts[MAX_PEBS_EVENTS] = {};
 	short error[MAX_PEBS_EVENTS] = {};
+	int bit, i;
 
 	if (!x86_pmu.pebs_active)
 		return;
@@ -1142,6 +1143,15 @@ static void intel_pmu_drain_pebs_nhm(str
 	for (at = base; at < top; at += x86_pmu.pebs_record_size) {
 		struct pebs_record_nhm *p = at;
 
+		/* PEBS v3 has accurate status bits */
+		if (x86_pmu.intel_cap.pebs_format >= 3) {
+			for_each_set_bit(bit, (unsigned long *)&p->status,
+					 MAX_PEBS_EVENTS)
+				counts[bit]++;
+
+			continue;
+		}
+
 		bit = find_first_bit((unsigned long *)&p->status,
 					x86_pmu.max_pebs_events);
 		if (bit >= x86_pmu.max_pebs_events)
@@ -1171,8 +1181,6 @@ static void intel_pmu_drain_pebs_nhm(str
 			pebs_status = p->status & cpuc->pebs_enabled;
 			pebs_status &= (1ULL << MAX_PEBS_EVENTS) - 1;
 			if (pebs_status != (1 << bit)) {
-				u8 i;
-
 				for_each_set_bit(i, (unsigned long *)&pebs_status,
 						 MAX_PEBS_EVENTS)
 					error[i]++;
--
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