perf_counter: per event wakeups

By request, provide a way to request a wakeup every 'n' events instead
of every page of output.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Orig-LKML-Reference: <20090402091319.323309784@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 995063df910f..9bcab10e735d 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1760,7 +1760,15 @@ static void perf_output_copy(struct perf_output_handle *handle,
 
 static void perf_output_end(struct perf_output_handle *handle)
 {
-        if (handle->wakeup)
+        int wakeup_events = handle->counter->hw_event.wakeup_events;
+
+        if (wakeup_events) {
+                int events = atomic_inc_return(&handle->data->events);
+                if (events >= wakeup_events) {
+                        atomic_sub(wakeup_events, &handle->data->events);
+                        __perf_output_wakeup(handle);
+                }
+        } else if (handle->wakeup)
                 __perf_output_wakeup(handle);
         rcu_read_unlock();
 }