lkml.org 
[lkml]   [2021]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 07/10] coresight: trbe: Do not truncate buffer on IRQ
Date
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
\
 
 \ /
  Last update: 2021-07-23 14:47    [W:0.293 / U:0.352 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site