[PATCH] x86, perf: Allow time stamp for free running PEBSv3

[PATCH] x86, perf: Allow time stamp for free running PEBSv3

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

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: kan.liang@intel.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 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(-)

diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index d1388fe..2860b89 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -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
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 626e7db..7ab1ba1 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -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
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index f7f28c3..22f236b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -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:
-- 
1.9.3

Re: [PATCH] x86, perf: Allow time stamp for free running PEBSv3

[Peter Zijlstra]

On Tue, May 12, 2015 at 11:11:48AM -0700, Andi Kleen wrote:
> +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).

> +		flags &= ~PERF_SAMPLE_TIME;
> +	return flags;
> +}