Re: [PATCH] perf stat: Disable NMI watchdog message on hybrid

[Jiri Olsa]

On Fri, May 28, 2021 at 11:55:47AM +0800, Jin Yao wrote:
> If we run a single workload that only runs on big core, there is always a
> ugly message about disabling the NMI watchdog because the atom is not
> counted.
> 
> Before:
> 
>   # perf stat ls
>   ...
> 
>    Performance counter stats for 'ls':
> 
>                 0.94 msec task-clock                #    0.620 CPUs utilized
>                    0      context-switches          #    0.000 /sec
>                    0      cpu-migrations            #    0.000 /sec
>                  111      page-faults               #  118.603 K/sec
>            3,111,368      cpu_core/cycles/          #    3.324 G/sec
>        <not counted>      cpu_atom/cycles/                                              (0.00%)
>            2,965,942      cpu_core/instructions/    #    3.169 G/sec
>        <not counted>      cpu_atom/instructions/                                        (0.00%)
>              596,579      cpu_core/branches/        #  637.442 M/sec
>        <not counted>      cpu_atom/branches/                                            (0.00%)
>               15,744      cpu_core/branch-misses/   #   16.822 M/sec
>        <not counted>      cpu_atom/branch-misses/                                       (0.00%)
> 
>          0.001509271 seconds time elapsed
> 
>          0.001572000 seconds user
>          0.000000000 seconds sys
> 
>   Some events weren't counted. Try disabling the NMI watchdog:
>           echo 0 > /proc/sys/kernel/nmi_watchdog
>           perf stat ...
>           echo 1 > /proc/sys/kernel/nmi_watchdog
> 
> Now we disable the NMI watchdog message on hybrid, otherwise there
> are too many false positives.
> 
> After:
> 
>   # perf stat ls
>   ...
> 
>    Performance counter stats for 'ls':
> 
>                 2.32 msec task-clock                #    0.712 CPUs utilized
>                    0      context-switches          #    0.000 /sec
>                    0      cpu-migrations            #    0.000 /sec
>                  110      page-faults               #   47.327 K/sec
>            2,313,349      cpu_core/cycles/          #  995.308 M/sec
>        <not counted>      cpu_atom/cycles/                                              (0.00%)
>            2,986,113      cpu_core/instructions/    #    1.285 G/sec
>        <not counted>      cpu_atom/instructions/                                        (0.00%)
>              598,861      cpu_core/branches/        #  257.657 M/sec
>        <not counted>      cpu_atom/branches/                                            (0.00%)
>               16,090      cpu_core/branch-misses/   #    6.923 M/sec
>        <not counted>      cpu_atom/branch-misses/                                       (0.00%)
> 
>          0.003265716 seconds time elapsed
> 
>          0.000000000 seconds user
>          0.003307000 seconds sys
> 
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

> ---
>  tools/perf/util/stat-display.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index b759dfd633b4..db3c7a105a2b 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -465,7 +465,8 @@ static void printout(struct perf_stat_config *config, struct aggr_cpu_id id, int
>  			config->csv_sep);
>  
>  		if (counter->supported) {
> -			config->print_free_counters_hint = 1;
> +			if (!perf_pmu__is_hybrid(counter->pmu_name))
> +				config->print_free_counters_hint = 1;
>  			if (is_mixed_hw_group(counter))
>  				config->print_mixed_hw_group_error = 1;
>  		}
> -- 
> 2.17.1
>