Re: [PATCH v2 1/2] perf evlist: Allow setting arbitrary leader

[Arnaldo Carvalho de Melo]

Em Thu, Nov 18, 2021 at 02:06:46PM -0800, Ian Rogers escreveu:
> The leader of a group is the first, but allow it to be an arbitrary
> list member so that for Intel topdown events slots may always be the
> group leader.
> 
> Reviewed-by: Kajol Jain<kjain@xxxxxxxxxxxxx>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
>  tools/lib/perf/evlist.c                  | 15 +++++++++------
>  tools/lib/perf/include/internal/evlist.h |  2 +-
>  tools/perf/util/parse-events.c           |  2 +-
>  3 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index e37dfad31383..974da341b8b0 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -643,14 +643,14 @@ perf_evlist__next_mmap(struct perf_evlist *evlist, struct perf_mmap *map,
>  	return overwrite ? evlist->mmap_ovw_first : evlist->mmap_first;
>  }
>  
> -void __perf_evlist__set_leader(struct list_head *list)
> +void __perf_evlist__set_leader(struct list_head *list, struct perf_evsel *leader)
>  {
> -	struct perf_evsel *evsel, *leader;
> +	struct perf_evsel *first, *last, *evsel;
>  
> -	leader = list_entry(list->next, struct perf_evsel, node);
> -	evsel = list_entry(list->prev, struct perf_evsel, node);
> +	first = list_entry(list->next, struct perf_evsel, node);
> +	last = list_entry(list->prev, struct perf_evsel, node);

We have list_first_entry() and list_last_entry():

For instance:

tools/perf/util/parse-events.c:	leader = list_first_entry(list, struct evsel, core.node);

Can we use it here?
  
> -	leader->nr_members = evsel->idx - leader->idx + 1;
> +	leader->nr_members = last->idx - first->idx + 1;
>  
>  	__perf_evlist__for_each_entry(list, evsel)
>  		evsel->leader = leader;
> @@ -659,7 +659,10 @@ void __perf_evlist__set_leader(struct list_head *list)
>  void perf_evlist__set_leader(struct perf_evlist *evlist)
>  {
>  	if (evlist->nr_entries) {
> +		struct perf_evsel *first = list_entry(evlist->entries.next,
> +						struct perf_evsel, node);
> +
>  		evlist->nr_groups = evlist->nr_entries > 1 ? 1 : 0;
> -		__perf_evlist__set_leader(&evlist->entries);
> +		__perf_evlist__set_leader(&evlist->entries, first);
>  	}
>  }
> diff --git a/tools/lib/perf/include/internal/evlist.h b/tools/lib/perf/include/internal/evlist.h
> index f366dbad6a88..6f74269a3ad4 100644
> --- a/tools/lib/perf/include/internal/evlist.h
> +++ b/tools/lib/perf/include/internal/evlist.h
> @@ -127,5 +127,5 @@ int perf_evlist__id_add_fd(struct perf_evlist *evlist,
>  
>  void perf_evlist__reset_id_hash(struct perf_evlist *evlist);
>  
> -void __perf_evlist__set_leader(struct list_head *list);
> +void __perf_evlist__set_leader(struct list_head *list, struct perf_evsel *leader);
>  #endif /* __LIBPERF_INTERNAL_EVLIST_H */
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 5bfb6f892489..6308ba739d19 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1834,8 +1834,8 @@ void parse_events__set_leader(char *name, struct list_head *list,
>  	if (parse_events__set_leader_for_uncore_aliase(name, list, parse_state))
>  		return;
>  
> -	__perf_evlist__set_leader(list);
>  	leader = list_entry(list->next, struct evsel, core.node);
> +	__perf_evlist__set_leader(list, &leader->core);
>  	leader->group_name = name ? strdup(name) : NULL;

Ditto

>  }
>  
> -- 
> 2.34.0.rc2.393.gf8c9666880-goog

-- 

- Arnaldo