Re: [PATCH 2/5] libperf: Propagate maps only if necessary

From: Adrian Hunter
Date: Mon Oct 03 2022 - 01:36:27 EST


On 30/09/22 20:27, Namhyung Kim wrote:
> The current code propagate evsel's cpu map settings to evlist when it's
> added to an evlist. But the evlist->all_cpus and each evsel's cpus will
> be updated in perf_evlist__set_maps() later. No need to do it before
> evlist's cpus are set actually.
>
> In fact it discards this intermediate all_cpus maps at the beginning
> of perf_evlist__set_maps(). Let's not do this. It's only needed when
> an evsel is added after the evlist cpu/thread maps are set.
>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/lib/perf/evlist.c | 8 ++++----
> tools/lib/perf/include/internal/evlist.h | 1 +
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index 187129652ab6..c5f65b89d77a 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -67,9 +67,7 @@ static void perf_evlist__propagate_maps(struct perf_evlist *evlist)
> {
> struct perf_evsel *evsel;
>
> - /* Recomputing all_cpus, so start with a blank slate. */
> - perf_cpu_map__put(evlist->all_cpus);
> - evlist->all_cpus = NULL;

If you remove this, then you also need to remove the setting in
perf_evlist__set_maps, so that we still start with a blank slate.
i.e.

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index 8ec5b9f344e0..4aeffcbc11d1 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -174,9 +174,6 @@ void perf_evlist__set_maps(struct perf_evlist *evlist,
evlist->threads = perf_thread_map__get(threads);
}

- if (!evlist->all_cpus && cpus)
- evlist->all_cpus = perf_cpu_map__get(cpus);
-
perf_evlist__propagate_maps(evlist);
}


> + evlist->needs_map_propagation = true;
>
> perf_evlist__for_each_evsel(evlist, evsel)
> __perf_evlist__propagate_maps(evlist, evsel);
> @@ -81,7 +79,9 @@ void perf_evlist__add(struct perf_evlist *evlist,
> evsel->idx = evlist->nr_entries;
> list_add_tail(&evsel->node, &evlist->entries);
> evlist->nr_entries += 1;
> - __perf_evlist__propagate_maps(evlist, evsel);
> +
> + if (evlist->needs_map_propagation)
> + __perf_evlist__propagate_maps(evlist, evsel);
> }
>
> void perf_evlist__remove(struct perf_evlist *evlist,
> diff --git a/tools/lib/perf/include/internal/evlist.h b/tools/lib/perf/include/internal/evlist.h
> index 6f89aec3e608..850f07070036 100644
> --- a/tools/lib/perf/include/internal/evlist.h
> +++ b/tools/lib/perf/include/internal/evlist.h
> @@ -19,6 +19,7 @@ struct perf_evlist {
> int nr_entries;
> int nr_groups;
> bool has_user_cpus;
> + bool needs_map_propagation;
> /**
> * The cpus passed from the command line or all online CPUs by
> * default.