perf_counter: counter overflow limit

Provide means to auto-disable the counter after 'n' overflow events.

Create the counter with hw_event.disabled = 1, and then issue an
ioctl(fd, PREF_COUNTER_IOC_REFRESH, n); to set the limit and enable
the counter.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094518.083139737@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 928a7fae0961..ef4dcbff75ab 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -155,8 +155,9 @@ struct perf_counter_hw_event {
 /*
  * Ioctls that can be done on a perf counter fd:
  */
-#define PERF_COUNTER_IOC_ENABLE         _IO('$', 0)
-#define PERF_COUNTER_IOC_DISABLE        _IO('$', 1)
+#define PERF_COUNTER_IOC_ENABLE         _IO ('$', 0)
+#define PERF_COUNTER_IOC_DISABLE        _IO ('$', 1)
+#define PERF_COUNTER_IOC_REFRESH        _IOW('$', 2, u32)
 
 /*
  * Structure of the page that can be mapped via mmap
@@ -403,9 +404,14 @@ struct perf_counter {
         /* poll related */
         wait_queue_head_t               waitq;
         struct fasync_struct            *fasync;
-        /* optional: for NMIs */
+
+        /* delayed work for NMIs and such */
+        int                             pending_wakeup;
+        int                             pending_disable;
         struct perf_pending_entry       pending;
 
+        atomic_t                        event_limit;
+
         void (*destroy)(struct perf_counter *);
         struct rcu_head                 rcu_head;
 #endif