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

[Wang, Weilin]

> -----Original Message-----
> From: Namhyung Kim <namhyung@xxxxxxxxxx>
> Sent: Thursday, March 28, 2024 10:46 PM
> To: Wang, Weilin <weilin.wang@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>; Arnaldo Carvalho de Melo
> <acme@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Ingo Molnar
> <mingo@xxxxxxxxxx>; Alexander Shishkin
> <alexander.shishkin@xxxxxxxxxxxxxxx>; Jiri Olsa <jolsa@xxxxxxxxxx>; Hunter,
> Adrian <adrian.hunter@xxxxxxxxx>; Kan Liang <kan.liang@xxxxxxxxxxxxxxx>;
> linux-perf-users@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Taylor, Perry
> <perry.taylor@xxxxxxxxx>; Alt, Samantha <samantha.alt@xxxxxxxxx>; Biggers,
> Caleb <caleb.biggers@xxxxxxxxx>
> Subject: Re: [RFC PATCH v5 1/6] perf stat: Parse and find tpebs events when
> parsing metrics to prepare for perf record sampling
> 
> 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"?

We decided to use R as the modifier for retire_latency in one of the previous 
version of code review. Therefore, the code searches for R instead of "retire_latency".

It should search for :R in usual cases. But in hybrid platform, event name might be in 
format like cpu_core@event_name@R. 

Thanks,
Weilin

> 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);