From: Kan Liang kan.liang@linux.intel.com
[ Upstream commit 07d85ba9d04e1ebd282f656a29ddf08c5b7b32a2 ]
Hundreds of "read LOST count failed" error messages may be displayed, when the below command is launched.
perf record -e '{cpu/mem-loads-aux/,cpu/event=0xcd,umask=0x1/}:S' -a
According to the commit 89e3106fa25fb1b6 ("libperf: Handle read format in perf_evsel__read()"), the PERF_FORMAT_GROUP is only available for the leader. However, the record__read_lost_samples() goes through every entry of an evlist, which includes both leader and member. The member event errors out and triggers the error message. Since there may be hundreds of CPUs on a server, the message will be printed hundreds of times, which is very annoying.
The message itself is correct, but the pr_err is a overkill. Other error messages in the record__read_lost_samples() are all pr_debug. To make the output format consistent, change the pr_err("read LOST count failed\n"); to pr_debug("read LOST count failed\n");. User can still get the message via -v option.
Fixes: e3a23261ad06d598 ("perf record: Read and inject LOST_SAMPLES events") Signed-off-by: Kan Liang kan.liang@linux.intel.com Acked-by: Namhyung Kim namhyung@kernel.org Cc: Ian Rogers irogers@google.com Cc: Ingo Molnar mingo@redhat.com Cc: Jiri Olsa jolsa@kernel.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Link: https://lore.kernel.org/r/20230301150413.27011-1-kan.liang@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/builtin-record.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 48c3461b496c4..7314183cdcb6c 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -1864,7 +1864,7 @@ static void __record__read_lost_samples(struct record *rec, struct evsel *evsel, int id_hdr_size;
if (perf_evsel__read(&evsel->core, cpu_idx, thread_idx, &count) < 0) { - pr_err("read LOST count failed\n"); + pr_debug("read LOST count failed\n"); return; }