[PATCH v2] perf arm-spe: Synthesize SPE instruction events

[Namhyung Kim]

Hello,

On Wed, Dec 15, 2021 at 10:46 AM German Gomez <german.gomez at arm.com> wrote:
>
> Synthesize instruction events per every decoded ARM SPE record.
>
> Because Arm SPE implements a hardware-based sample period, and perf
> implements a software-based one that gets applied on top, also add a
> warning to make the user aware.
>
> Signed-off-by: German Gomez <german.gomez at arm.com>
> ---
> Changes since v1 [https://lore.kernel.org/all/20211117142833.226629-1-german.gomez@arm.com]
>   - Generate events with "--itrace=i" instead of "--itrace=o".
>   - Generate events with virt_addr, phys_addr, and data_src values.
> ---
>  tools/perf/util/arm-spe.c | 58 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
>
> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> index fccac06b573a..879583822c8f 100644
> --- a/tools/perf/util/arm-spe.c
> +++ b/tools/perf/util/arm-spe.c
> @@ -58,6 +58,8 @@ struct arm_spe {
>         u8                              sample_branch;
>         u8                              sample_remote_access;
>         u8                              sample_memory;
> +       u8                              sample_instructions;
> +       u64                             instructions_sample_period;
>
>         u64                             l1d_miss_id;
>         u64                             l1d_access_id;
> @@ -68,6 +70,7 @@ struct arm_spe {
>         u64                             branch_miss_id;
>         u64                             remote_access_id;
>         u64                             memory_id;
> +       u64                             instructions_id;
>
>         u64                             kernel_start;
>
> @@ -90,6 +93,7 @@ struct arm_spe_queue {
>         u64                             time;
>         u64                             timestamp;
>         struct thread                   *thread;
> +       u64                             period_instructions;
>  };
>
>  static void arm_spe_dump(struct arm_spe *spe __maybe_unused,
> @@ -202,6 +206,7 @@ static struct arm_spe_queue *arm_spe__alloc_queue(struct arm_spe *spe,
>         speq->pid = -1;
>         speq->tid = -1;
>         speq->cpu = -1;
> +       speq->period_instructions = 0;
>
>         /* params set */
>         params.get_trace = arm_spe_get_trace;
> @@ -351,6 +356,33 @@ static int arm_spe__synth_branch_sample(struct arm_spe_queue *speq,
>         return arm_spe_deliver_synth_event(spe, speq, event, &sample);
>  }
>
> +static int arm_spe__synth_instruction_sample(struct arm_spe_queue *speq,
> +                                            u64 spe_events_id, u64 data_src)
> +{
> +       struct arm_spe *spe = speq->spe;
> +       struct arm_spe_record *record = &speq->decoder->record;
> +       union perf_event *event = speq->event_buf;
> +       struct perf_sample sample = { .ip = 0, };
> +
> +       /*
> +        * Handles perf instruction sampling period.
> +        */
> +       speq->period_instructions++;
> +       if (speq->period_instructions < spe->instructions_sample_period)
> +               return 0;
> +       speq->period_instructions = 0;
> +
> +       arm_spe_prep_sample(spe, speq, event, &sample);
> +
> +       sample.id = spe_events_id;
> +       sample.stream_id = spe_events_id;
> +       sample.addr = record->virt_addr;
> +       sample.phys_addr = record->phys_addr;
> +       sample.data_src = data_src;

I think it should set sample.period to spe->instructions_sample_period.

Also it can set sample.weight but I think we lost my patch

  https://lore.kernel.org/r/20211201220855.1260688-1-namhyung@kernel.org

Arnaldo, can you please take a look?

> +
> +       return arm_spe_deliver_synth_event(spe, speq, event, &sample);
> +}
> +
>  #define SPE_MEM_TYPE   (ARM_SPE_L1D_ACCESS | ARM_SPE_L1D_MISS | \
>                          ARM_SPE_LLC_ACCESS | ARM_SPE_LLC_MISS | \
>                          ARM_SPE_REMOTE_ACCESS)
> @@ -480,6 +512,12 @@ static int arm_spe_sample(struct arm_spe_queue *speq)
>                         return err;
>         }
>
> +       if (spe->sample_instructions) {
> +               err = arm_spe__synth_instruction_sample(speq, spe->instructions_id, data_src);
> +               if (err)
> +                       return err;
> +       }
> +
>         return 0;
>  }
>
> @@ -1107,6 +1145,26 @@ arm_spe_synth_events(struct arm_spe *spe, struct perf_session *session)
>                         return err;
>                 spe->memory_id = id;
>                 arm_spe_set_event_name(evlist, id, "memory");
> +               id += 1;
> +       }
> +
> +       if (spe->synth_opts.instructions) {
> +               if (spe->synth_opts.period_type != PERF_ITRACE_PERIOD_INSTRUCTIONS)
> +                       return -EINVAL;
> +
> +               if (spe->synth_opts.period > 1)
> +                       pr_warning("Arm SPE has a hardware-based sample period.\n"
> +                                  "More instruction events will be discarded by --itrace\n");
> +
> +               spe->sample_instructions = true;
> +               attr.config = PERF_COUNT_HW_INSTRUCTIONS;
> +               attr.sample_period = spe->synth_opts.period;
> +               spe->instructions_sample_period = attr.sample_period;
> +               err = arm_spe_synth_event(session, &attr, id);
> +               if (err)
> +                       return err;
> +               spe->instructions_id = id;
> +               arm_spe_set_event_name(evlist, id, "instructions");

Yeah, I think it's a better name than "all". :)

Thanks,
Namhyung


>         }
>
>         return 0;
> --
> 2.25.1
>