[PATCH 08/10] perf/core: Add PERF_AUX_FLAG_COLLISION to report colliding samples
From: robin.murphy@arm.com (Robin Murphy)
Date: 2017-03-31 16:44:30
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Hi Will, On 27/01/17 18:07, Will Deacon wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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..68a4e542968e 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 0x03 /* sample collided with another */
Does COLLISION really represent the combination of both TRUNCATED and OVERWRITE, or does that want to be 0x04? (The way they get ORed together at one point in the following patch makes me suspicious.) Robin.
#define PERF_FLAG_FD_NO_GROUP (1UL << 0) #define PERF_FLAG_FD_OUTPUT (1UL << 1)