perf_counter: Allow for a wakeup watermark
Currently we wake the mmap() consumer once every PAGE_SIZE of data
and/or once event wakeup_events when specified.
For high speed sampling this results in too many wakeups wrt. the
buffer size, hence change this.
We move the default wakeup limit to 1/4-th the buffer size, and
provide for means to manually specify this limit.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 972f90d..6c1ef72 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -199,10 +199,14 @@
inherit_stat : 1, /* per task counts */
enable_on_exec : 1, /* next exec enables */
task : 1, /* trace fork/exit */
+ watermark : 1, /* wakeup_watermark */
- __reserved_1 : 50;
+ __reserved_1 : 49;
- __u32 wakeup_events; /* wakeup every n events */
+ union {
+ __u32 wakeup_events; /* wakeup every n events */
+ __u32 wakeup_watermark; /* bytes before wakeup */
+ };
__u32 __reserved_2;
__u64 __reserved_3;
@@ -521,6 +525,8 @@
atomic_t wakeup; /* needs a wakeup */
atomic_t lost; /* nr records lost */
+ long watermark; /* wakeup watermark */
+
struct perf_counter_mmap_page *user_page;
void *data_pages[0];
};
