[PATCH v2 4/6] perf/core: Add PERF_AUX_FLAG_COLLISION to report colliding samples

From: Will Deacon
Date: Thu Apr 06 2017 - 12:18:34 EST


The ARM SPE architecture permits an implementation to ignore a sample
if the sample is due to be taken whilst another sample is already being
produced. In this case, it is desirable to report the collision to
userspace, as they may want to lower the sample period.

This patch adds a PERF_AUX_FLAG_COLLISION flag, so that such events can
be relayed to userspace.

Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
---
include/uapi/linux/perf_event.h | 1 +
1 file changed, 1 insertion(+)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index c66a485a24ac..f4e3a21cade5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -885,6 +885,7 @@ enum perf_callchain_context {
*/
#define PERF_AUX_FLAG_TRUNCATED 0x01 /* record was truncated to fit */
#define PERF_AUX_FLAG_OVERWRITE 0x02 /* snapshot from overwrite mode */
+#define PERF_AUX_FLAG_COLLISION 0x08 /* sample collided with another */

#define PERF_FLAG_FD_NO_GROUP (1UL << 0)
#define PERF_FLAG_FD_OUTPUT (1UL << 1)
--
2.1.4