Re: [RFC PATCH v5 1/6] perf stat: Parse and find tpebs events when parsing metrics to prepare for perf record sampling

[Namhyung Kim]

On Tue, Mar 26, 2024 at 1:29 PM <weilin.wang@xxxxxxxxx> wrote:
>
> From: Weilin Wang <weilin.wang@xxxxxxxxx>
>
> Metrics that use tpebs values would use the :retire_latency keyword in
> formulas. We put all these events into a list and pass the list to perf
> record to collect their retire latency value.
>
> Signed-off-by: Weilin Wang <weilin.wang@xxxxxxxxx>
> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
[SNIP]
> @@ -681,8 +685,56 @@ static int metricgroup__build_event_string(struct strbuf *events,
>         hashmap__for_each_entry(ctx->ids, cur, bkt) {
>                 const char *sep, *rsep, *id = cur->pkey;
>                 enum perf_tool_event ev;
> +               /*
> +                * Parse and search for event name with retire_latency modifier.
> +                * If found, put event name into the tpebs_events list. This list
> +                * of events will be passed to perf record for sampling to get
> +                * their reitre_latency value.
> +                * Search for ":R" in event name without "@". Search for the
> +                * last "@R" in event name with "@".

What is the retire_latency modifier exactly?
Why do you search for :R and @R?  What's the difference?
Why don't you search for "retire_latency"?

Thanks,
Namhyung


> +                */
> +               char *p = strstr(id, ":R");
> +               char *p1 = strstr(id, "@R");
> +
> +               if (p == NULL && p1) {
> +                       p = strstr(p1+1, "@R");
> +                       if (p == NULL)
> +                               p = p1;
> +                       p = p+1;
> +               }
> +
> +               if (p) {
> +                       char *name;
> +                       char *at;
> +                       struct tpebs_event *new_event = malloc(sizeof(struct tpebs_event));
>
> -               pr_debug("found event %s\n", id);
> +                       if (!new_event)
> +                               return -ENOMEM;
> +
> +                       new_event->tpebs_name = strdup(id);
> +                       *p = '\0';
> +                       name = malloc(strlen(id) + 2);
> +                       if (!name)
> +                               return -ENOMEM;
> +
> +                       at = strchr(id, '@');
> +                       if (at != NULL) {
> +                               *at = '/';
> +                               at = strchr(id, '@');
> +                               *at = '/';
> +                               strcpy(name, id);
> +                               strcat(name, "p");
> +                       } else {
> +                               strcpy(name, id);
> +                               strcat(name, ":p");
> +                       }
> +                       new_event->name = name;
> +                       *tpebs_event_size += 1;
> +                       pr_debug("retire_latency required, tpebs_event_size=%lu, new_event=%s\n",
> +                               *tpebs_event_size, new_event->name);
> +                       list_add_tail(&new_event->nd, tpebs_events);
> +                       continue;
> +               }
>
>                 /* Always move tool events outside of the group. */
>                 ev = perf_tool_event__from_str(id);