Re: [PATCH] perf stat: Skip duration_time in setup_system_wide

Arnaldo Carvalho de Melo
2020-09-22T17:56:34Z

Em Tue, Sep 22, 2020 at 09:50:04AM +0800, Jin Yao escreveu:
> Some metrics (such as DRAM_BW_Use) consists of uncore events and
> duration_time. For uncore events, counter->core.system_wide is
> true. But for duration_time, counter->core.system_wide is false
> so target.system_wide is set to false.
>
> Then 'enable_on_exec' is set in perf_event_attr of uncore event.
> Kernel will return error when trying to open the uncore event.
>
> This patch skips the duration_time in setup_system_wide then
> target.system_wide will be set to true for the evlist of uncore
> events + duration_time.
>
> Before (tested on skylake desktop):
>
> # perf stat -M DRAM_BW_Use -- sleep 1
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (arb/event=0x84,umask=0x1/).
> /bin/dmesg | grep -i perf may provide additional information.
>
> After:
>
> # perf stat -M DRAM_BW_Use -- sleep 1
>
> Performance counter stats for 'system wide':
>
> 169 arb/event=0x84,umask=0x1/ # 0.00 DRAM_BW_Use
> 40,427 arb/event=0x81,umask=0x1/
> 1,000,902,197 ns duration_time
>
> 1.000902197 seconds time elapsed
>
> Fixes: 648b5af3f3ae ("libperf: Move 'system_wide' from 'struct evsel' to 'struct perf_evsel'")

Humm, what makes you think that this cset was the one introducing this
problem? It just moves evsel->system_wide to evsel->core.system_wide.

- Arnaldo

> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
> ---
> tools/perf/builtin-stat.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 7f8d756d9408..9bcc93bc0973 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2047,8 +2047,10 @@ static void setup_system_wide(int forks)
> struct evsel *counter;
>
> evlist__for_each_entry(evsel_list, counter) {
> - if (!counter->core.system_wide)
> + if (!counter->core.system_wide &&
> + strcmp(counter->name, "duration_time")) {
> return;
> + }
> }
>
> if (evsel_list->core.nr_entries)
> --
> 2.17.1
>

--

- Arnaldo