Date:   Thu, 1 Sep 2022 22:29:12 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Kan Liang <kan.liang@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Stephane Eranian <eranian@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>, andreas.kogler.0x@...il.com,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH V2 4/6] perf: Use sample_flags for weight

On Thu, Sep 1, 2022 at 6:10 AM <kan.liang@...ux.intel.com> wrote:
>
> From: Kan Liang <kan.liang@...ux.intel.com>
>
> Use the new sample_flags to indicate whether the weight field is filled
> by the PMU driver.
>
> Remove the weight field from the perf_sample_data_init() to minimize the
> number of cache lines touched.
>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> ---
>  arch/powerpc/perf/core-book3s.c |  5 +++--
>  arch/x86/events/intel/ds.c      | 10 +++++++---
>  include/linux/perf_event.h      |  3 +--
>  kernel/events/core.c            |  3 +++
>  4 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index 1ad1efdb33f9..a5c95a2006ea 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -2305,9 +2305,10 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
>                         ppmu->get_mem_data_src(&data.data_src, ppmu->flags, regs);
>
>                 if (event->attr.sample_type & PERF_SAMPLE_WEIGHT_TYPE &&
> -                                               ppmu->get_mem_weight)
> +                                               ppmu->get_mem_weight) {
>                         ppmu->get_mem_weight(&data.weight.full, event->attr.sample_type);
> -
> +                       data.sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
> +               }
>                 if (perf_event_overflow(event, &data, regs))
>                         power_pmu_stop(event, 0);
>         } else if (period) {
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index 5dcfd2de6ef8..f66a4905cc87 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -1535,8 +1535,10 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
>         /*
>          * Use latency for weight (only avail with PEBS-LL)
>          */
> -       if (fll && (sample_type & PERF_SAMPLE_WEIGHT_TYPE))
> +       if (fll && (sample_type & PERF_SAMPLE_WEIGHT_TYPE)) {
>                 data->weight.full = pebs->lat;
> +               data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
> +       }
>
>         /*
>          * data.data_src encodes the data source
> @@ -1628,9 +1630,10 @@ static void setup_pebs_fixed_sample_data(struct perf_event *event,
>
>         if (x86_pmu.intel_cap.pebs_format >= 2) {
>                 /* Only set the TSX weight when no memory weight. */
> -               if ((sample_type & PERF_SAMPLE_WEIGHT_TYPE) && !fll)
> +               if ((sample_type & PERF_SAMPLE_WEIGHT_TYPE) && !fll) {
>                         data->weight.full = intel_get_tsx_weight(pebs->tsx_tuning);
> -
> +                       data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;
> +               }
>                 if (sample_type & PERF_SAMPLE_TRANSACTION)
>                         data->txn = intel_get_tsx_transaction(pebs->tsx_tuning,
>                                                               pebs->ax);
> @@ -1772,6 +1775,7 @@ static void setup_pebs_adaptive_sample_data(struct perf_event *event,
>                                 data->weight.var1_dw = (u32)(weight & PEBS_LATENCY_MASK) ?:
>                                         intel_get_tsx_weight(meminfo->tsx_tuning);
>                         }
> +                       data->sample_flags |= PERF_SAMPLE_WEIGHT_TYPE;

I was thinking about splitting PERF_SAMPLE_WEIGHT and
PERF_SAMPLE_WEIGHT_STRUCT but it'd just add complexity
unnecessarily?

Thanks,
Namhyung

>                 }
>
>                 if (sample_type & PERF_SAMPLE_DATA_SRC)
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 1e12e79454e0..06a587b5faa9 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1012,7 +1012,6 @@ struct perf_sample_data {
>         u64                             addr;
>         struct perf_raw_record          *raw;
>         u64                             period;
> -       union perf_sample_weight        weight;
>         u64                             txn;
>         union  perf_mem_data_src        data_src;
>
> @@ -1021,6 +1020,7 @@ struct perf_sample_data {
>          * perf_{prepare,output}_sample().
>          */
>         struct perf_branch_stack        *br_stack;
> +       union perf_sample_weight        weight;
>
>         u64                             type;
>         u64                             ip;
> @@ -1063,7 +1063,6 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
>         data->addr = addr;
>         data->raw  = NULL;
>         data->period = period;
> -       data->weight.full = 0;
>         data->data_src.val = PERF_MEM_NA;
>         data->txn = 0;
>  }
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 104c0c9f4e6f..f0af45db02b3 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7408,6 +7408,9 @@ void perf_prepare_sample(struct perf_event_header *header,
>                 header->size += size;
>         }
>
> +       if (filtered_sample_type & PERF_SAMPLE_WEIGHT_TYPE)
> +               data->weight.full = 0;
> +
>         if (sample_type & PERF_SAMPLE_REGS_INTR) {
>                 /* regs dump ABI info */
>                 int size = sizeof(u64);
> --
> 2.35.1
>

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