Messages in this thread Patch in this message |  | | From | Suzuki K Poulose <> | Subject | [PATCH v2 07/10] coresight: trbe: Do not truncate buffer on IRQ | Date | Fri, 23 Jul 2021 13:46:08 +0100 |
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The TRBE driver marks the AUX buffer as TRUNCATED when we get an IRQ on FILL event. This has rather unwanted side-effect of the event being disabled when there may be more space in the ring buffer.
So, instead of TRUNCATE we need a different flag to indicate that the trace may have lost a few bytes (i.e from the point of generating the FILL event until the IRQ is consumed). Anyways, the userspace must use the size from RECORD_AUX headers to restrict the "trace" decoding.
Using PARTIAL flag causes the perf tool to generate the following warning:
Warning: AUX data had gaps in it XX times out of YY!
Are you running a KVM guest in the background?
which is pointlessly scary for a user. The other remaining options are : - COLLISION - Use by SPE to indicate samples collided - Add a new flag - Specifically for CoreSight, doesn't sound so good, if we can re-use something.
Given that we don't already use the "COLLISION" flag, the above behavior can be notified using this flag for CoreSight.
Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: James Clark <james.clark@arm.com> Cc: Mike Leach <mike.leach@linaro.org> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Leo Yan <leo.yan@linaro.org> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> --- drivers/hwtracing/coresight/coresight-trbe.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c index 503bea0137ae..d50f142e86d1 100644 --- a/drivers/hwtracing/coresight/coresight-trbe.c +++ b/drivers/hwtracing/coresight/coresight-trbe.c @@ -615,7 +615,7 @@ static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev, * for correct size. Also, mark the buffer truncated. */ write = get_trbe_limit_pointer(); - perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED); + perf_aux_output_flag(handle, PERF_AUX_FLAG_COLLISION); } offset = write - base; @@ -708,7 +708,7 @@ static void trbe_handle_overflow(struct perf_output_handle *handle) * collection upon the WRAP event, without stopping the source. */ perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW | - PERF_AUX_FLAG_TRUNCATED); + PERF_AUX_FLAG_COLLISION); perf_aux_output_end(handle, size); event_data = perf_aux_output_begin(handle, event); if (!event_data) { -- 2.24.1
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