Re: [PATCH v1 06/14] libperf cpumap: Add any, empty and min helpers

[Ian Rogers]

On Tue, Dec 12, 2023 at 6:01 AM James Clark <james.clark@xxxxxxx> wrote:
>
>
>
> On 29/11/2023 06:02, Ian Rogers wrote:
> > Additional helpers to better replace
> > perf_cpu_map__has_any_cpu_or_is_empty.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> >  tools/lib/perf/cpumap.c              | 27 +++++++++++++++++++++++++++
> >  tools/lib/perf/include/perf/cpumap.h | 16 ++++++++++++++++
> >  tools/lib/perf/libperf.map           |  4 ++++
> >  3 files changed, 47 insertions(+)
> >
> > diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> > index 49fc98e16514..7403819da8fd 100644
> > --- a/tools/lib/perf/cpumap.c
> > +++ b/tools/lib/perf/cpumap.c
> > @@ -316,6 +316,19 @@ bool perf_cpu_map__has_any_cpu_or_is_empty(const struct perf_cpu_map *map)
> >       return map ? __perf_cpu_map__cpu(map, 0).cpu == -1 : true;
> >  }
> >
> > +bool perf_cpu_map__is_any_cpu_or_is_empty(const struct perf_cpu_map *map)
> > +{
> > +     if (!map)
> > +             return true;
> > +
> > +     return __perf_cpu_map__nr(map) == 1 && __perf_cpu_map__cpu(map, 0).cpu == -1;
> > +}
> > +
> > +bool perf_cpu_map__is_empty(const struct perf_cpu_map *map)
> > +{
> > +     return map == NULL;
> > +}
> > +
>
> Maybe it doesn't currently happen, but it seems a bit weird that the
> 'new' function can create a map of length 0 which would return empty ==
> false here.
>
> Could we either make this check also return true for maps with length 0,
> or prevent the new function from returning a map of 0 length?

We can add an assert or return NULL for size 0 in alloc. I think I
prefer the return NULL option. It should never happen but it feels the
right defensive thing to do.

Thanks,
Ian

> >  int perf_cpu_map__idx(const struct perf_cpu_map *cpus, struct perf_cpu cpu)
> >  {
> >       int low, high;
> > @@ -372,6 +385,20 @@ bool perf_cpu_map__has_any_cpu(const struct perf_cpu_map *map)
> >       return map && __perf_cpu_map__cpu(map, 0).cpu == -1;
> >  }
> >
> > +struct perf_cpu perf_cpu_map__min(const struct perf_cpu_map *map)
> > +{
> > +     struct perf_cpu cpu, result = {
> > +             .cpu = -1
> > +     };
> > +     int idx;
> > +
> > +     perf_cpu_map__for_each_cpu_skip_any(cpu, idx, map) {
> > +             result = cpu;
> > +             break;
> > +     }
> > +     return result;
> > +}
> > +
> >  struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map)
> >  {
> >       struct perf_cpu result = {
> > diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
> > index dbe0a7352b64..523e4348fc96 100644
> > --- a/tools/lib/perf/include/perf/cpumap.h
> > +++ b/tools/lib/perf/include/perf/cpumap.h
> > @@ -50,6 +50,22 @@ LIBPERF_API int perf_cpu_map__nr(const struct perf_cpu_map *cpus);
> >   * perf_cpu_map__has_any_cpu_or_is_empty - is map either empty or has the "any CPU"/dummy value.
> >   */
> >  LIBPERF_API bool perf_cpu_map__has_any_cpu_or_is_empty(const struct perf_cpu_map *map);
> > +/**
> > + * perf_cpu_map__is_any_cpu_or_is_empty - is map either empty or the "any CPU"/dummy value.
> > + */
> > +LIBPERF_API bool perf_cpu_map__is_any_cpu_or_is_empty(const struct perf_cpu_map *map);
> > +/**
> > + * perf_cpu_map__is_empty - does the map contain no values and it doesn't
> > + *                          contain the special "any CPU"/dummy value.
> > + */
> > +LIBPERF_API bool perf_cpu_map__is_empty(const struct perf_cpu_map *map);
> > +/**
> > + * perf_cpu_map__min - the minimum CPU value or -1 if empty or just the "any CPU"/dummy value.
> > + */
> > +LIBPERF_API struct perf_cpu perf_cpu_map__min(const struct perf_cpu_map *map);
> > +/**
> > + * perf_cpu_map__max - the maximum CPU value or -1 if empty or just the "any CPU"/dummy value.
> > + */
> >  LIBPERF_API struct perf_cpu perf_cpu_map__max(const struct perf_cpu_map *map);
> >  LIBPERF_API bool perf_cpu_map__has(const struct perf_cpu_map *map, struct perf_cpu cpu);
> >  LIBPERF_API bool perf_cpu_map__equal(const struct perf_cpu_map *lhs,
> > diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> > index 10b3f3722642..2aa79b696032 100644
> > --- a/tools/lib/perf/libperf.map
> > +++ b/tools/lib/perf/libperf.map
> > @@ -10,6 +10,10 @@ LIBPERF_0.0.1 {
> >               perf_cpu_map__nr;
> >               perf_cpu_map__cpu;
> >               perf_cpu_map__has_any_cpu_or_is_empty;
> > +             perf_cpu_map__is_any_cpu_or_is_empty;
> > +             perf_cpu_map__is_empty;
> > +             perf_cpu_map__has_any_cpu;
> > +             perf_cpu_map__min;
> >               perf_cpu_map__max;
> >               perf_cpu_map__has;
> >               perf_thread_map__new_array;