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x86, perf: Allow time stamp for free running PEBSv3

PATCH In review Andi Kleen 2 participants 2 messages May 12, 2015

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x86 perf events
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Andi Kleen

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PATCH 1/1 x86, perf: Allow time stamp for free running PEBSv3

From: Andi Kleen <[email protected]>

With PEBSv3 the PEBS record contains a time stamp. That means we can allow free-running PEBS without a PMI even if the user program requested a time stamp. This avoids the need to use -T to get free running PEBS, and also avoids any problems with mis-identifying MMAPs later.

Move the free_running_flags state into a variable in x86_pmu and use it. This only works when no explicit clock_id is set.

Cc [email protected]
Signed-off-by Andi Kleen <[email protected]>
---
 arch/x86/kernel/cpu/perf_event.h          |  1 +
 arch/x86/kernel/cpu/perf_event_intel.c    | 15 ++++++++++++++-
 arch/x86/kernel/cpu/perf_event_intel_ds.c |  1 +
 3 files changed, 16 insertions(+), 1 deletion(-)
arch/x86/kernel/cpu/perf_event.h +1 -0
index d1388fe..2860b89 100644
@@ -589,6 +589,7 @@ struct x86_pmu {
 	struct event_constraint *pebs_constraints;
 	void		(*pebs_aliases)(struct perf_event *event);
 	int 		max_pebs_events;
+	unsigned long	free_running_flags;
 
 	/*
 	 * Intel LBR
arch/x86/kernel/cpu/perf_event_intel.c +14 -1
index 626e7db..7ab1ba1 100644
@@ -2507,6 +2507,15 @@ static void intel_pebs_aliases_snb(struct perf_event *event)
 	}
 }
 
+static unsigned long intel_pmu_free_running_flags(struct perf_event *event)
+{
+	unsigned long flags = x86_pmu.free_running_flags;
+
+	if (event->attr.clockid)
+		flags &= ~PERF_SAMPLE_TIME;
+	return flags;
+}
+
 static int intel_pmu_hw_config(struct perf_event *event)
 {
 	int ret = x86_pmu_hw_config(event);

@@ -2517,7 +2526,8 @@ static int intel_pmu_hw_config(struct perf_event *event)
 	if (event->attr.precise_ip) {
 		if (!event->attr.freq) {
 			event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
-			if (!(event->attr.sample_type & ~PEBS_FREERUNNING_FLAGS))
+			if (!(event->attr.sample_type &
+			      ~intel_pmu_free_running_flags(event)))
 				event->hw.flags |= PERF_X86_EVENT_FREERUNNING;
 		}
 		if (x86_pmu.pebs_aliases)

@@ -2954,6 +2964,8 @@ static __initconst const struct x86_pmu core_pmu = {
 	.event_map		= intel_pmu_event_map,
 	.max_events		= ARRAY_SIZE(intel_perfmon_event_map),
 	.apic			= 1,
+	.free_running_flags	= PEBS_FREERUNNING_FLAGS,
+
 	/*
 	 * Intel PMCs cannot be accessed sanely above 32-bit width,
 	 * so we install an artificial 1<<31 period regardless of

@@ -2992,6 +3004,7 @@ static __initconst const struct x86_pmu intel_pmu = {
 	.event_map		= intel_pmu_event_map,
 	.max_events		= ARRAY_SIZE(intel_perfmon_event_map),
 	.apic			= 1,
+	.free_running_flags	= PEBS_FREERUNNING_FLAGS,
 	/*
 	 * Intel PMCs cannot be accessed sanely above 32 bit width,
 	 * so we install an artificial 1<<31 period regardless of
arch/x86/kernel/cpu/perf_event_intel_ds.c +1 -0
index f7f28c3..22f236b 100644
@@ -1295,6 +1295,7 @@ void __init intel_ds_init(void)
 			x86_pmu.pebs_record_size =
 						sizeof(struct pebs_record_skl);
 			x86_pmu.drain_pebs = intel_pmu_drain_pebs_nhm;
+			x86_pmu.free_running_flags |= PERF_SAMPLE_TIME;
 			break;
 
 		default:
Signature · 1 line
1.9.3
maintainer
#1 lore raw

arch/x86/kernel/cpu/perf_event_intel.c static void intel_pebs_aliases_snb(struct perf_event *event) · line 2514

Quoted 5 lines · Andi Kleen
arch/x86/kernel/cpu/perf_event_intel.c +5 -0
+static unsigned long intel_pmu_free_running_flags(struct perf_event *event)
+{
+	unsigned long flags = x86_pmu.free_running_flags;
+
+	if (event->attr.clockid)

Made that: use_clockid, otherwise CLOCK_REALTIME would still allow this (if it were allowed with hardware events).

Quoted 3 lines
arch/x86/kernel/cpu/perf_event_intel.c +3 -0
+		flags &= ~PERF_SAMPLE_TIME;
+	return flags;
+}