oprofile: Implement performance counter multiplexing

The number of hardware counters is limited. The multiplexing feature
enables OProfile to gather more events than counters are provided by
the hardware. This is realized by switching between events at an user
specified time interval.

A new file (/dev/oprofile/time_slice) is added for the user to specify
the timer interval in ms. If the number of events to profile is higher
than the number of hardware counters available, the patch will
schedule a work queue that switches the event counter and re-writes
the different sets of values into it. The switching mechanism needs to
be implemented for each architecture to support multiplexing. This
patch only implements AMD CPU support, but multiplexing can be easily
extended for other models and architectures.

There are follow-on patches that rework parts of this patch.

Signed-off-by: Jason Yeh <jason.yeh@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/oprofile/oprofile_stats.c b/drivers/oprofile/oprofile_stats.c
index 3c2270a..77a57a6 100644
--- a/drivers/oprofile/oprofile_stats.c
+++ b/drivers/oprofile/oprofile_stats.c
@@ -16,6 +16,9 @@
 #include "cpu_buffer.h"
 
 struct oprofile_stat_struct oprofile_stats;
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+atomic_t multiplex_counter;
+#endif
 
 void oprofile_reset_stats(void)
 {
@@ -34,6 +37,9 @@ void oprofile_reset_stats(void)
 	atomic_set(&oprofile_stats.sample_lost_no_mapping, 0);
 	atomic_set(&oprofile_stats.event_lost_overflow, 0);
 	atomic_set(&oprofile_stats.bt_lost_no_mapping, 0);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	atomic_set(&multiplex_counter, 0);
+#endif
 }
 
 
@@ -76,4 +82,8 @@ void oprofile_create_stats_files(struct super_block *sb, struct dentry *root)
 		&oprofile_stats.event_lost_overflow);
 	oprofilefs_create_ro_atomic(sb, dir, "bt_lost_no_mapping",
 		&oprofile_stats.bt_lost_no_mapping);
+#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
+	oprofilefs_create_ro_atomic(sb, dir, "multiplex_counter",
+		&multiplex_counter);
+#endif
 }