[PATCH v7 07/10] perf record --off-cpu: Disable perf_event's callchain collection

[Howard Chu <howardchu95@gmail.com>]

There is a check in evsel.c that does this:

if (evsel__is_offcpu_event(evsel))
	evsel->core.attr.sample_type &= OFFCPU_SAMPLE_TYPES;

This along with:

 #define OFFCPU_SAMPLE_TYPES  (PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_IP | \
			      PERF_SAMPLE_TID | PERF_SAMPLE_TIME | \
			      PERF_SAMPLE_ID | PERF_SAMPLE_CPU | \
			      PERF_SAMPLE_PERIOD | PERF_SAMPLE_CALLCHAIN | \
			      PERF_SAMPLE_CGROUP)

will tell perf_event to collect callchain.

We don't need the callchain from perf_event when collecting off-cpu
samples, because it's prev's callchain, not next's callchain.

   (perf_event)     (task_storage) (needed)
   prev             next
   |                  |
   ---sched_switch---->

Signed-off-by: Howard Chu <howardchu95@gmail.com>
---
 tools/perf/util/off_cpu.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/off_cpu.h b/tools/perf/util/off_cpu.h
index c6edc0f7c40d..f07ab2e36317 100644
--- a/tools/perf/util/off_cpu.h
+++ b/tools/perf/util/off_cpu.h
@@ -13,7 +13,7 @@ struct record_opts;
 #define OFFCPU_SAMPLE_TYPES  (PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_IP | \
 			      PERF_SAMPLE_TID | PERF_SAMPLE_TIME | \
 			      PERF_SAMPLE_ID | PERF_SAMPLE_CPU | \
-			      PERF_SAMPLE_PERIOD | PERF_SAMPLE_CALLCHAIN | \
+			      PERF_SAMPLE_PERIOD | PERF_SAMPLE_RAW | \
 			      PERF_SAMPLE_CGROUP)
 
 #define OFFCPU_THRESH 500000ull
-- 
2.43.0