Re: [PATCH v2 4/4] perf report: Add 'simd' sort field

[Ian Rogers <irogers@google.com>]

On Mon, Mar 20, 2023 at 8:15 AM James Clark <james.clark@arm.com> wrote:
>
> From: German Gomez <german.gomez@arm.com>
>
> Add 'simd' sort field to visualize SIMD ops in perf-report.
>
> Rows are labeled with the SIMD isa, and the type of predicate (if any):
>
>   - [p] partial predicate
>   - [e] empty predicate (no elements in the vector being used)
>
> Example with Arm SPE and SVE (Scalable Vector Extension):
>
>   #include <arm_sve.h>
>
>   double src[1025], dst[1025];
>
>   int main(void) {
>     svfloat64_t vc = svdup_f64(1);
>     for(;;)
>       for(int i = 0; i < 1025; i += svcntd())
>       {
>         svbool_t pg = svwhilelt_b64(i, 1025);
>         svfloat64_t vsrc = svld1(pg, &src[i]);
>         svfloat64_t vdst = svadd_x(pg, vsrc, vc);
>         svst1(pg, &dst[i], vdst);
>       }
>     return 0;
>   }
>
>   ... compiled using "gcc-11 -march=armv8-a+sve -O3"
>
> Profiling on a platform that implements FEAT_SVE and FEAT_SPEv1p1:
>
>   $ perf record -e arm_spe_0// -- ./a.out
>   $ perf report --itrace=i1i -s overhead,pid,simd,sym
>
>   Overhead      Pid:Command   Simd     Symbol
>   ........  ................  .......  ......................
>
>     53.76%    10758:program            [.] main
>     46.14%    10758:program   [.] SVE  [.] main
>      0.09%    10758:program   [p] SVE  [.] main
>
> The report shows 0.09% of the sampled SVE operations use partial
> predicates due to src and dst arrays not being multiples of the vector
> register lengths.
>
> Signed-off-by: German Gomez <german.gomez@arm.com>
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>  tools/perf/Documentation/perf-report.txt |  1 +
>  tools/perf/util/hist.c                   |  1 +
>  tools/perf/util/hist.h                   |  1 +
>  tools/perf/util/sort.c                   | 47 ++++++++++++++++++++++++
>  tools/perf/util/sort.h                   |  2 +
>  5 files changed, 52 insertions(+)
>
> diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
> index c242e8da6b1a..cfd502f7e6da 100644
> --- a/tools/perf/Documentation/perf-report.txt
> +++ b/tools/perf/Documentation/perf-report.txt
> @@ -117,6 +117,7 @@ OPTIONS
>         - addr: (Full) virtual address of the sampled instruction
>         - retire_lat: On X86, this reports pipeline stall of this instruction compared
>           to the previous instruction in cycles. And currently supported only on X86
> +       - simd: Flags describing a SIMD operation. "e" for empty Arm SVE predicate. "p" for partial Arm SVE predicate

nit: the line wrap looks off here.

Thanks,
Ian

>
>         By default, comm, dso and symbol keys are used.
>         (i.e. --sort comm,dso,symbol)
> diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
> index 3670136a0074..0c11f50abfec 100644
> --- a/tools/perf/util/hist.c
> +++ b/tools/perf/util/hist.c
> @@ -745,6 +745,7 @@ __hists__add_entry(struct hists *hists,
>                 .weight = sample->weight,
>                 .ins_lat = sample->ins_lat,
>                 .p_stage_cyc = sample->p_stage_cyc,
> +               .simd_flags = sample->simd_flags,
>         }, *he = hists__findnew_entry(hists, &entry, al, sample_self);
>
>         if (!hists->has_callchains && he && he->callchain_size != 0)
> diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
> index 86a677954279..afc9f1c7f4dc 100644
> --- a/tools/perf/util/hist.h
> +++ b/tools/perf/util/hist.h
> @@ -81,6 +81,7 @@ enum hist_column {
>         HISTC_ADDR_FROM,
>         HISTC_ADDR_TO,
>         HISTC_ADDR,
> +       HISTC_SIMD,
>         HISTC_NR_COLS, /* Last entry */
>  };
>
> diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
> index 093a0c8b2e3d..e11e68ecf0a2 100644
> --- a/tools/perf/util/sort.c
> +++ b/tools/perf/util/sort.c
> @@ -139,6 +139,52 @@ struct sort_entry sort_thread = {
>         .se_width_idx   = HISTC_THREAD,
>  };
>
> +/* --sort simd */
> +
> +static int64_t
> +sort__simd_cmp(struct hist_entry *left, struct hist_entry *right)
> +{
> +       if (left->simd_flags.arch != right->simd_flags.arch)
> +               return (int64_t) left->simd_flags.arch - right->simd_flags.arch;
> +
> +       return (int64_t) left->simd_flags.pred - right->simd_flags.pred;
> +}
> +
> +static const char *hist_entry__get_simd_name(struct simd_flags *simd_flags)
> +{
> +       u64 arch = simd_flags->arch;
> +
> +       if (arch & SIMD_OP_FLAGS_ARCH_SVE)
> +               return "SVE";
> +       else
> +               return "n/a";
> +}
> +
> +static int hist_entry__simd_snprintf(struct hist_entry *he, char *bf,
> +                                    size_t size, unsigned int width __maybe_unused)
> +{
> +       const char *name;
> +
> +       if (!he->simd_flags.arch)
> +               return repsep_snprintf(bf, size, "");
> +
> +       name = hist_entry__get_simd_name(&he->simd_flags);
> +
> +       if (he->simd_flags.pred & SIMD_OP_FLAGS_PRED_EMPTY)
> +               return repsep_snprintf(bf, size, "[e] %s", name);
> +       else if (he->simd_flags.pred & SIMD_OP_FLAGS_PRED_PARTIAL)
> +               return repsep_snprintf(bf, size, "[p] %s", name);
> +
> +       return repsep_snprintf(bf, size, "[.] %s", name);
> +}
> +
> +struct sort_entry sort_simd = {
> +       .se_header      = "Simd   ",
> +       .se_cmp         = sort__simd_cmp,
> +       .se_snprintf    = hist_entry__simd_snprintf,
> +       .se_width_idx   = HISTC_SIMD,
> +};
> +
>  /* --sort comm */
>
>  /*
> @@ -2142,6 +2188,7 @@ static struct sort_dimension common_sort_dimensions[] = {
>         DIM(SORT_ADDR, "addr", sort_addr),
>         DIM(SORT_LOCAL_RETIRE_LAT, "local_retire_lat", sort_local_p_stage_cyc),
>         DIM(SORT_GLOBAL_RETIRE_LAT, "retire_lat", sort_global_p_stage_cyc),
> +       DIM(SORT_SIMD, "simd", sort_simd)
>  };
>
>  #undef DIM
> diff --git a/tools/perf/util/sort.h b/tools/perf/util/sort.h
> index 22f437c3476f..ecfb7f1359d5 100644
> --- a/tools/perf/util/sort.h
> +++ b/tools/perf/util/sort.h
> @@ -111,6 +111,7 @@ struct hist_entry {
>         u64                     p_stage_cyc;
>         u8                      cpumode;
>         u8                      depth;
> +       struct simd_flags       simd_flags;
>
>         /* We are added by hists__add_dummy_entry. */
>         bool                    dummy;
> @@ -241,6 +242,7 @@ enum sort_type {
>         SORT_ADDR,
>         SORT_LOCAL_RETIRE_LAT,
>         SORT_GLOBAL_RETIRE_LAT,
> +       SORT_SIMD,
>
>         /* branch stack specific sort keys */
>         __SORT_BRANCH_STACK,
> --
> 2.34.1
>

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