[tip:perfcounters/core] perf_counter: Log irq_period changes

[tip-bot for Peter Zijlstra <a.p.zijlstra@chello.nl>]

Commit-ID:  26b119bc811a73bac6ecf95bdf284bf31c7955f0
Gitweb:     http://git.kernel.org/tip/26b119bc811a73bac6ecf95bdf284bf31c7955f0
Author:     Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Wed, 20 May 2009 12:21:20 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 20 May 2009 12:43:33 +0200

perf_counter: Log irq_period changes

For the dynamic irq_period code, log whenever we change the period so that
analyzing code can normalize the event flow.

[ Impact: add new feature to allow more precise profiling ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090520102553.298769743@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 include/linux/perf_counter.h |    8 ++++++++
 kernel/perf_counter.c        |   40 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c8c1dfc..f612941 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -258,6 +258,14 @@ enum perf_event_type {
 	PERF_EVENT_COMM			= 3,
 
 	/*
+	 * struct {
+	 * 	struct perf_event_header	header;
+	 * 	u64				irq_period;
+	 * };
+	 */
+	PERF_EVENT_PERIOD		= 4,
+
+	/*
 	 * When header.misc & PERF_EVENT_MISC_OVERFLOW the event_type field
 	 * will be PERF_RECORD_*
 	 *
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 64113e6..db02eb1 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1046,7 +1046,9 @@ int perf_counter_task_enable(void)
 	return 0;
 }
 
-void perf_adjust_freq(struct perf_counter_context *ctx)
+static void perf_log_period(struct perf_counter *counter, u64 period);
+
+static void perf_adjust_freq(struct perf_counter_context *ctx)
 {
 	struct perf_counter *counter;
 	u64 irq_period;
@@ -1072,6 +1074,8 @@ void perf_adjust_freq(struct perf_counter_context *ctx)
 		if (!irq_period)
 			irq_period = 1;
 
+		perf_log_period(counter, irq_period);
+
 		counter->hw.irq_period = irq_period;
 		counter->hw.interrupts = 0;
 	}
@@ -2407,6 +2411,40 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
 }
 
 /*
+ *
+ */
+
+static void perf_log_period(struct perf_counter *counter, u64 period)
+{
+	struct perf_output_handle handle;
+	int ret;
+
+	struct {
+		struct perf_event_header	header;
+		u64				time;
+		u64				period;
+	} freq_event = {
+		.header = {
+			.type = PERF_EVENT_PERIOD,
+			.misc = 0,
+			.size = sizeof(freq_event),
+		},
+		.time = sched_clock(),
+		.period = period,
+	};
+
+	if (counter->hw.irq_period == period)
+		return;
+
+	ret = perf_output_begin(&handle, counter, sizeof(freq_event), 0, 0);
+	if (ret)
+		return;
+
+	perf_output_put(&handle, freq_event);
+	perf_output_end(&handle);
+}
+
+/*
  * Generic counter overflow handling.
  */