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>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c8c1dfc2..f612941 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -258,6 +258,14 @@
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 @@
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 @@
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 @@
}
/*
+ *
+ */
+
+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.
*/
