linux-kernel - Re: [PATCH V3 1/5] perf/core: Add PERF_SAMPLE_WEIGHT

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Date:   Thu, 4 Feb 2021 23:00:23 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Yao Jin <yao.jin@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>, maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH V3 1/5] perf/core: Add PERF_SAMPLE_WEIGHT_STRUCT

Hi Kan,

On Sat, Jan 30, 2021 at 2:25 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
[SNIP]
> diff --git a/include/uapi/linux/perf_event.h
> b/include/uapi/linux/perf_event.h
> index b15e344..c50718a 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -145,12 +145,14 @@ enum perf_event_sample_format {
>         PERF_SAMPLE_CGROUP                      = 1U << 21,
>         PERF_SAMPLE_DATA_PAGE_SIZE              = 1U << 22,
>         PERF_SAMPLE_CODE_PAGE_SIZE              = 1U << 23,
> +       PERF_SAMPLE_WEIGHT_STRUCT               = 1U << 24,
>
> -       PERF_SAMPLE_MAX = 1U << 24,             /* non-ABI */
> +       PERF_SAMPLE_MAX = 1U << 25,             /* non-ABI */
>
>         __PERF_SAMPLE_CALLCHAIN_EARLY           = 1ULL << 63, /* non-ABI; internal use */
>   };
>
> +#define PERF_SAMPLE_WEIGHT_TYPE        (PERF_SAMPLE_WEIGHT |
> PERF_SAMPLE_WEIGHT_STRUCT)

I'm not sure you want to expose it in the uapi header as it's not
intended to be used IMHO.

Thanks,
Namhyung


>   /*
>    * values to program into branch_sample_type when PERF_SAMPLE_BRANCH
> is set
>    *
> @@ -890,7 +892,25 @@ enum perf_event_type {
>          *        char                  data[size];
>          *        u64                   dyn_size; } && PERF_SAMPLE_STACK_USER
>          *
> -        *      { u64                   weight;   } && PERF_SAMPLE_WEIGHT
> +        *      { union perf_sample_weight
> +        *       {
> +        *              u64             full; && PERF_SAMPLE_WEIGHT
> +        *      #if defined(__LITTLE_ENDIAN_BITFIELD)
> +        *              struct {
> +        *                      u32     var1_dw;
> +        *                      u16     var2_w;
> +        *                      u16     var3_w;
> +        *              } && PERF_SAMPLE_WEIGHT_STRUCT
> +        *      #elif defined(__BIG_ENDIAN_BITFIELD)
> +        *              struct {
> +        *                      u16     var3_w;
> +        *                      u16     var2_w;
> +        *                      u32     var1_dw;
> +        *              } && PERF_SAMPLE_WEIGHT_STRUCT
> +        *      #endif
> +        *
> +        *       }
> +        *      }
>          *      { u64                   data_src; } && PERF_SAMPLE_DATA_SRC
>          *      { u64                   transaction; } && PERF_SAMPLE_TRANSACTION
>          *      { u64                   abi; # enum perf_sample_regs_abi
> @@ -1248,4 +1268,29 @@ struct perf_branch_entry {
>                 reserved:40;
>   };
>
> +#if defined(__LITTLE_ENDIAN_BITFIELD)
> +union perf_sample_weight {
> +       __u64           full;
> +       struct {
> +               __u32   var1_dw;
> +               __u16   var2_w;
> +               __u16   var3_w;
> +       };
> +};
> +
> +#elif defined(__BIG_ENDIAN_BITFIELD)
> +
> +union perf_sample_weight {
> +       __u64           full;
> +       struct {
> +               __u16   var3_w;
> +               __u16   var2_w;
> +               __u32   var1_dw;
> +       };
> +};
> +
> +#else
> +#error "Unknown endianness"
> +#endif
> +
>   #endif /* _UAPI_LINUX_PERF_EVENT_H */