[PATCH 07/18] perf record: Support weak groups

Arnaldo Carvalho de Melo
2018-11-06T12:06:56Z

From: Andi Kleen <ak@linux.intel.com>

Implement a weak group fallback for 'perf record', similar to the
existing 'perf stat' support. This allows to use groups that might be
longer than the available counters without failing.

Before:

$ perf record -e '{cycles,cache-misses,cache-references,cpu_clk_unhalted.thread,cycles,cycles,cycles}' -a sleep 1
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cycles).
/bin/dmesg | grep -i perf may provide additional information.

After:

$ ./perf record -e '{cycles,cache-misses,cache-references,cpu_clk_unhalted.thread,cycles,cycles,cycles}:W' -a sleep 1
WARNING: No sample_id_all support, falling back to unordered processing
[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 8.136 MB perf.data (134069 samples) ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20181001195927.14211-2-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/Documentation/perf-list.txt | 1 -
tools/perf/builtin-record.c | 7 ++++++-
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt
index 236b9b97dfdb..667c14e56031 100644
--- a/tools/perf/Documentation/perf-list.txt
+++ b/tools/perf/Documentation/perf-list.txt
@@ -55,7 +55,6 @@ counted. The following modifiers exist:
S - read sample value (PERF_SAMPLE_READ)
D - pin the event to the PMU
W - group is weak and will fallback to non-group if not schedulable,
- only supported in 'perf stat' for now.

The 'p' modifier can be used for specifying how precise the instruction
address should be. The 'p' modifier can be specified multiple times:
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 10cf889c6d75..488779bc4c8d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -391,7 +391,12 @@ static int record__open(struct record *rec)
ui__warning("%s\n", msg);
goto try_again;
}
-
+ if ((errno == EINVAL || errno == EBADF) &&
+ pos->leader != pos &&
+ pos->weak_group) {
+ pos = perf_evlist__reset_weak_group(evlist, pos);
+ goto try_again;
+ }
rc = -errno;
perf_evsel__open_strerror(pos, &opts->target,
errno, msg, sizeof(msg));
--
2.14.4