Subject: Re: [PATCH] perflib: deprecate bpf_map__resize in favor of bpf_map_set_max_entries

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Wed, 15 Sep 2021 17:56:26 -0300

Em Mon, Aug 16, 2021 at 12:28:14PM -0700, Andrii Nakryiko escreveu:
> On Sun, Aug 15, 2021 at 3:36 AM Muhammad Falak R Wani
> <[email-masked]> wrote:
> >
> > As a part of libbpf 1.0 plan[0], this patch deprecates use of
> > bpf_map__resize in favour of bpf_map__set_max_entries.
> >
> > Reference: https://github.com/libbpf/libbpf/issues/304
> > [0]: https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0#libbpfh-high-level-apis
> >
> > Signed-off-by: Muhammad Falak R Wani <[email-masked]>
> > ---
> 
> All looks good, there is an opportunity to simplify the code a bit (see below).
> 
> Arnaldo, I assume you'll take this through your tree or you'd like us

Yeah, I'll take the opportunity to try to improve that detection of
libbpf version, etc.

- Arnaldo

> to take it through bpf-next?
> 
> Acked-by: Andrii Nakryiko <[email-masked]>
> 
> >  tools/perf/util/bpf_counter.c        | 8 ++++----
> >  tools/perf/util/bpf_counter_cgroup.c | 8 ++++----
> >  2 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
> > index ba0f20853651..ced2dac31dcf 100644
> > --- a/tools/perf/util/bpf_counter.c
> > +++ b/tools/perf/util/bpf_counter.c
> > @@ -127,9 +127,9 @@ static int bpf_program_profiler_load_one(struct evsel *evsel, u32 prog_id)
> >
> >         skel->rodata->num_cpu = evsel__nr_cpus(evsel);
> >
> > -       bpf_map__resize(skel->maps.events, evsel__nr_cpus(evsel));
> > -       bpf_map__resize(skel->maps.fentry_readings, 1);
> > -       bpf_map__resize(skel->maps.accum_readings, 1);
> > +       bpf_map__set_max_entries(skel->maps.events, evsel__nr_cpus(evsel));
> > +       bpf_map__set_max_entries(skel->maps.fentry_readings, 1);
> > +       bpf_map__set_max_entries(skel->maps.accum_readings, 1);
> >
> >         prog_name = bpf_target_prog_name(prog_fd);
> >         if (!prog_name) {
> > @@ -399,7 +399,7 @@ static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd,
> >                 return -1;
> >         }
> >
> > -       bpf_map__resize(skel->maps.events, libbpf_num_possible_cpus());
> > +       bpf_map__set_max_entries(skel->maps.events, libbpf_num_possible_cpus());
> 
> If you set max_entries to 0 (or just skip specifying it) for events
> map in util/bpf_skel/bperf_cgroup.bpf.c, you won't need to resize it,
> libbpf will automatically size it to number of possible CPUs.
> 
> >         err = bperf_leader_bpf__load(skel);
> >         if (err) {
> >                 pr_err("Failed to load leader skeleton\n");
> > diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c
> > index 89aa5e71db1a..cbc6c2bca488 100644
> > --- a/tools/perf/util/bpf_counter_cgroup.c
> > +++ b/tools/perf/util/bpf_counter_cgroup.c
> > @@ -65,14 +65,14 @@ static int bperf_load_program(struct evlist *evlist)
> >
> >         /* we need one copy of events per cpu for reading */
> >         map_size = total_cpus * evlist->core.nr_entries / nr_cgroups;
> > -       bpf_map__resize(skel->maps.events, map_size);
> > -       bpf_map__resize(skel->maps.cgrp_idx, nr_cgroups);
> > +       bpf_map__set_max_entries(skel->maps.events, map_size);
> > +       bpf_map__set_max_entries(skel->maps.cgrp_idx, nr_cgroups);
> >         /* previous result is saved in a per-cpu array */
> >         map_size = evlist->core.nr_entries / nr_cgroups;
> > -       bpf_map__resize(skel->maps.prev_readings, map_size);
> > +       bpf_map__set_max_entries(skel->maps.prev_readings, map_size);
> >         /* cgroup result needs all events (per-cpu) */
> >         map_size = evlist->core.nr_entries;
> > -       bpf_map__resize(skel->maps.cgrp_readings, map_size);
> > +       bpf_map__set_max_entries(skel->maps.cgrp_readings, map_size);
> >
> >         set_max_rlimit();
> >
> > --
> > 2.17.1
> >

-- 

- Arnaldo