Re: [PATCH v1 02/14] libperf cpumap: Rename and prefer sysfs for perf_cpu_map__default_new

[Ian Rogers]

On Tue, Dec 12, 2023 at 9:39 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> wrote:
>
> Em Tue, Nov 28, 2023 at 10:01:59PM -0800, Ian Rogers escreveu:
> > Rename perf_cpu_map__default_new to perf_cpu_map__new_online_cpus to
> > better indicate what the implementation does. Read the online CPUs
> > from /sys/devices/system/cpu/online first before using sysconf as
> > sysconf can't accurately configure holes in the CPU map. If sysconf is
> > used, warn when the configured and online processors disagree.
> >
> > When reading from a file, if the read doesn't yield a CPU map then
> > return an empty map rather than the default online. This avoids
> > recursion but also better yields being able to detect failures.
> >
> > Add more comments.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> >  tools/lib/perf/cpumap.c              | 59 +++++++++++++++++-----------
> >  tools/lib/perf/include/perf/cpumap.h | 15 ++++++-
> >  tools/lib/perf/libperf.map           |  2 +-
> >  tools/lib/perf/tests/test-cpumap.c   |  2 +-
> >  4 files changed, 51 insertions(+), 27 deletions(-)
> >
> > diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> > index 2bd6aba3d8c9..463ca8b37d45 100644
> > --- a/tools/lib/perf/cpumap.c
> > +++ b/tools/lib/perf/cpumap.c
> > @@ -9,6 +9,7 @@
> >  #include <unistd.h>
> >  #include <ctype.h>
> >  #include <limits.h>
> > +#include "internal.h"
> >
> >  void perf_cpu_map__set_nr(struct perf_cpu_map *map, int nr_cpus)
> >  {
> > @@ -66,15 +67,21 @@ void perf_cpu_map__put(struct perf_cpu_map *map)
> >       }
> >  }
> >
> > -static struct perf_cpu_map *cpu_map__default_new(void)
> > +static struct perf_cpu_map *cpu_map__new_sysconf(void)
> >  {
> >       struct perf_cpu_map *cpus;
> > -     int nr_cpus;
> > +     int nr_cpus, nr_cpus_conf;
> >
> >       nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> >       if (nr_cpus < 0)
> >               return NULL;
> >
> > +     nr_cpus_conf = sysconf(_SC_NPROCESSORS_CONF);
> > +     if (nr_cpus != nr_cpus_conf) {
> > +             pr_warning("Number of online CPUs (%d) differs from the number configured (%d) the CPU map will only cover the first %d CPUs.",
> > +                     nr_cpus, nr_cpus_conf, nr_cpus);
> > +     }
> > +
> >       cpus = perf_cpu_map__alloc(nr_cpus);
> >       if (cpus != NULL) {
> >               int i;
> > @@ -86,9 +93,27 @@ static struct perf_cpu_map *cpu_map__default_new(void)
> >       return cpus;
> >  }
> >
> > -struct perf_cpu_map *perf_cpu_map__default_new(void)
> > +static struct perf_cpu_map *cpu_map__new_syfs_online(void)
>
> I'm renaming this to cpu_map__new_sysfs_online(), ok?

Yep, typo. Thanks!

Ian

> - Arnaldo
>
> >  {
> > -     return cpu_map__default_new();
> > +     struct perf_cpu_map *cpus = NULL;
> > +     FILE *onlnf;
> > +
> > +     onlnf = fopen("/sys/devices/system/cpu/online", "r");
> > +     if (onlnf) {
> > +             cpus = perf_cpu_map__read(onlnf);
> > +             fclose(onlnf);
> > +     }
> > +     return cpus;
> > +}
> > +
> > +struct perf_cpu_map *perf_cpu_map__new_online_cpus(void)
> > +{
> > +     struct perf_cpu_map *cpus = cpu_map__new_syfs_online();
> > +
> > +     if (cpus)
> > +             return cpus;
> > +
> > +     return cpu_map__new_sysconf();
> >  }
> >
> >
> > @@ -180,27 +205,11 @@ struct perf_cpu_map *perf_cpu_map__read(FILE *file)
> >
> >       if (nr_cpus > 0)
> >               cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
> > -     else
> > -             cpus = cpu_map__default_new();
> >  out_free_tmp:
> >       free(tmp_cpus);
> >       return cpus;
> >  }
> >
> > -static struct perf_cpu_map *cpu_map__read_all_cpu_map(void)
> > -{
> > -     struct perf_cpu_map *cpus = NULL;
> > -     FILE *onlnf;
> > -
> > -     onlnf = fopen("/sys/devices/system/cpu/online", "r");
> > -     if (!onlnf)
> > -             return cpu_map__default_new();
> > -
> > -     cpus = perf_cpu_map__read(onlnf);
> > -     fclose(onlnf);
> > -     return cpus;
> > -}
> > -
> >  struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
> >  {
> >       struct perf_cpu_map *cpus = NULL;
> > @@ -211,7 +220,7 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
> >       int max_entries = 0;
> >
> >       if (!cpu_list)
> > -             return cpu_map__read_all_cpu_map();
> > +             return perf_cpu_map__new_online_cpus();
> >
> >       /*
> >        * must handle the case of empty cpumap to cover
> > @@ -268,9 +277,11 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
> >
> >       if (nr_cpus > 0)
> >               cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
> > -     else if (*cpu_list != '\0')
> > -             cpus = cpu_map__default_new();
> > -     else
> > +     else if (*cpu_list != '\0') {
> > +             pr_warning("Unexpected characters at end of cpu list ('%s'), using online CPUs.",
> > +                        cpu_list);
> > +             cpus = perf_cpu_map__new_online_cpus();
> > +     } else
> >               cpus = perf_cpu_map__new_any_cpu();
> >  invalid:
> >       free(tmp_cpus);
> > diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
> > index d0bf218ada11..b24bd8b8f34e 100644
> > --- a/tools/lib/perf/include/perf/cpumap.h
> > +++ b/tools/lib/perf/include/perf/cpumap.h
> > @@ -22,7 +22,20 @@ struct perf_cpu_map;
> >   * perf_cpu_map__new_any_cpu - a map with a singular "any CPU"/dummy -1 value.
> >   */
> >  LIBPERF_API struct perf_cpu_map *perf_cpu_map__new_any_cpu(void);
> > -LIBPERF_API struct perf_cpu_map *perf_cpu_map__default_new(void);
> > +/**
> > + * perf_cpu_map__new_online_cpus - a map read from
> > + *                                 /sys/devices/system/cpu/online if
> > + *                                 available. If reading wasn't possible a map
> > + *                                 is created using the online processors
> > + *                                 assuming the first 'n' processors are all
> > + *                                 online.
> > + */
> > +LIBPERF_API struct perf_cpu_map *perf_cpu_map__new_online_cpus(void);
> > +/**
> > + * perf_cpu_map__new - create a map from the given cpu_list such as "0-7". If no
> > + *                     cpu_list argument is provided then
> > + *                     perf_cpu_map__new_online_cpus is returned.
> > + */
> >  LIBPERF_API struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list);
> >  LIBPERF_API struct perf_cpu_map *perf_cpu_map__read(FILE *file);
> >  LIBPERF_API struct perf_cpu_map *perf_cpu_map__get(struct perf_cpu_map *map);
> > diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> > index a8ff64baea3e..8a71f841498e 100644
> > --- a/tools/lib/perf/libperf.map
> > +++ b/tools/lib/perf/libperf.map
> > @@ -2,7 +2,7 @@ LIBPERF_0.0.1 {
> >       global:
> >               libperf_init;
> >               perf_cpu_map__new_any_cpu;
> > -             perf_cpu_map__default_new;
> > +             perf_cpu_map__new_online_cpus;
> >               perf_cpu_map__get;
> >               perf_cpu_map__put;
> >               perf_cpu_map__new;
> > diff --git a/tools/lib/perf/tests/test-cpumap.c b/tools/lib/perf/tests/test-cpumap.c
> > index 2c359bdb951e..c998b1dae863 100644
> > --- a/tools/lib/perf/tests/test-cpumap.c
> > +++ b/tools/lib/perf/tests/test-cpumap.c
> > @@ -29,7 +29,7 @@ int test_cpumap(int argc, char **argv)
> >       perf_cpu_map__put(cpus);
> >       perf_cpu_map__put(cpus);
> >
> > -     cpus = perf_cpu_map__default_new();
> > +     cpus = perf_cpu_map__new_online_cpus();
> >       if (!cpus)
> >               return -1;
> >
> > --
> > 2.43.0.rc1.413.gea7ed67945-goog
> >
>
> --
>
> - Arnaldo