linux-kernel - Re: [PATCH] perf stat: Skip duration_time in setup_system

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Date:   Tue, 22 Sep 2020 14:56:30 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     jolsa@...nel.org, peterz@...radead.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
        ak@...ux.intel.com, kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf stat: Skip duration_time in setup_system_wide

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@...ux.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