Re: [PATCH v4 10/17] perf pmu-events: Hide pmu_events_map

[Ian Rogers]

On Fri, Aug 5, 2022 at 5:31 AM John Garry <john.garry@xxxxxxxxxx> wrote:
>
> On 04/08/2022 23:18, Ian Rogers wrote:
> > Move usage of the table to pmu-events.c so it may be hidden. By
> > abstracting the table the implementation can later be changed.
> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> >   tools/perf/pmu-events/empty-pmu-events.c |  81 ++++++++-
> >   tools/perf/pmu-events/jevents.py         |  81 ++++++++-
> >   tools/perf/pmu-events/pmu-events.h       |  29 +--
> >   tools/perf/tests/pmu-events.c            | 218 +++++++++++------------
> >   tools/perf/util/metricgroup.c            |  15 +-
> >   tools/perf/util/pmu.c                    |  34 +---
> >   tools/perf/util/pmu.h                    |   2 +-
> >   7 files changed, 280 insertions(+), 180 deletions(-)
> >
> > diff --git a/tools/perf/pmu-events/empty-pmu-events.c b/tools/perf/pmu-events/empty-pmu-events.c
> > index 216ea0482c37..8ef75aff996c 100644
> > --- a/tools/perf/pmu-events/empty-pmu-events.c
> > +++ b/tools/perf/pmu-events/empty-pmu-events.c
> > @@ -6,6 +6,8 @@
> >    * The test cpu/soc is provided for testing.
> >    */
> >   #include "pmu-events/pmu-events.h"
> > +#include "util/header.h"
> > +#include "util/pmu.h"
> >   #include <string.h>
> >   #include <stddef.h>
> >
> > @@ -110,7 +112,26 @@ static const struct pmu_event pme_test_soc_cpu[] = {
> >       },
> >   };
> >
> > -const struct pmu_events_map pmu_events_map[] = {
> > +
> > +/*
> > + * Map a CPU to its table of PMU events. The CPU is identified by the
> > + * cpuid field, which is an arch-specific identifier for the CPU.
> > + * The identifier specified in tools/perf/pmu-events/arch/xxx/mapfile
> > + * must match the get_cpuid_str() in tools/perf/arch/xxx/util/header.c)
> > + *
> > + * The  cpuid can contain any character other than the comma.
> > + */
> > +struct pmu_events_map {
> > +     const char *arch;
> > +     const char *cpuid;
> > +     const struct pmu_event *table;
> > +};
> > +
> > +/*
> > + * Global table mapping each known CPU for the architecture to its
> > + * table of PMU events.
> > + */
> > +static const struct pmu_events_map pmu_events_map[] = {
> >       {
> >               .arch = "testarch",
> >               .cpuid = "testcpu",
> > @@ -162,6 +183,62 @@ static const struct pmu_sys_events pmu_sys_event_tables[] = {
> >       },
> >   };
> >
> > +const struct pmu_event *perf_pmu__find_table(struct perf_pmu *pmu)
> > +{
> > +     const struct pmu_event *table = NULL;
> > +     char *cpuid = perf_pmu__getcpuid(pmu);
> > +     int i;
> > +
> > +     /* on some platforms which uses cpus map, cpuid can be NULL for
> > +      * PMUs other than CORE PMUs.
> > +      */
> > +     if (!cpuid)
> > +             return NULL;
> > +
> > +     i = 0;
> > +     for (;;) {
> > +             const struct pmu_events_map *map = &pmu_events_map[i++];
> > +
> > +             if (!map->table)
> > +                     break;
> > +
> > +             if (!strcmp_cpuid_str(map->cpuid, cpuid)) {
> > +                     table = map->table;
> > +                     break;
> > +             }
> > +     }
> > +     free(cpuid);
> > +     return table;
> > +}
> > +
> > +const struct pmu_event *find_core_events_table(const char *arch, const char *cpuid)
> > +{
> > +     for (const struct pmu_events_map *tables = &pmu_events_map[0];
> > +          tables->table;
> > +          tables++) {
> > +             if (!strcmp(tables->arch, arch) && !strcmp_cpuid_str(tables->cpuid, cpuid))
> > +                     return tables->table;
> > +     }
> > +     return NULL;
> > +}
> > +
> > +int pmu_for_each_core_event(pmu_event_iter_fn fn, void *data)
> > +{
> > +     for (const struct pmu_events_map *tables = &pmu_events_map[0];
> > +          tables->table;
> > +          tables++) {
> > +             for (const struct pmu_event *pe = &tables->table[0];
> > +                  pe->name || pe->metric_group || pe->metric_name;
> > +                  pe++) {
> > +                     int ret = fn(pe, &tables->table[0], data);
> > +
> > +                     if (ret)
> > +                             return ret;
> > +             }
> > +     }
> > +     return 0;
> > +}
> > +
> >   const struct pmu_event *find_sys_events_table(const char *name)
> >   {
> >       for (const struct pmu_sys_events *tables = &pmu_sys_event_tables[0];
> > @@ -181,7 +258,7 @@ int pmu_for_each_sys_event(pmu_event_iter_fn fn, void *data)
> >               for (const struct pmu_event *pe = &tables->table[0];
> >                    pe->name || pe->metric_group || pe->metric_name;
> >                    pe++) {
> > -                     int ret = fn(pe, data);
> > +                     int ret = fn(pe, &tables->table[0], data);
> >
> >                       if (ret)
> >                               return ret;
> > diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> > index dd21bc9eeeed..e976c5e8e80b 100755
> > --- a/tools/perf/pmu-events/jevents.py
> > +++ b/tools/perf/pmu-events/jevents.py
> > @@ -333,7 +333,27 @@ def process_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
> >
> >   def print_mapping_table(archs: Sequence[str]) -> None:
> >     """Read the mapfile and generate the struct from cpuid string to event table."""
> > -  _args.output_file.write('const struct pmu_events_map pmu_events_map[] = {\n')
> > +  _args.output_file.write("""
> > +/*
> > + * Map a CPU to its table of PMU events. The CPU is identified by the
> > + * cpuid field, which is an arch-specific identifier for the CPU.
> > + * The identifier specified in tools/perf/pmu-events/arch/xxx/mapfile
> > + * must match the get_cpuid_str() in tools/perf/arch/xxx/util/header.c)
> > + *
> > + * The  cpuid can contain any character other than the comma.
> > + */
> > +struct pmu_events_map {
> > +        const char *arch;
> > +        const char *cpuid;
> > +        const struct pmu_event *table;
> > +};
> > +
> > +/*
> > + * Global table mapping each known CPU for the architecture to its
> > + * table of PMU events.
> > + */
> > +const struct pmu_events_map pmu_events_map[] = {
> > +""")
> >     for arch in archs:
> >       if arch == 'test':
> >         _args.output_file.write("""{
> > @@ -389,6 +409,61 @@ static const struct pmu_sys_events pmu_sys_event_tables[] = {
> >   \t},
> >   };
> >
> > +const struct pmu_event *perf_pmu__find_table(struct perf_pmu *pmu)
> > +{
> > +        const struct pmu_event *table = NULL;
> > +        char *cpuid = perf_pmu__getcpuid(pmu);
>
> This seems an identical implementation to that in empty-pmu-events.c -
> can we reduce this duplication? Maybe a seperate common c file which can
> be linked in
>
> The indentation seems different also - this version seems to use whitespaces

Agreed. Later on this will change, the empty version isn't compressed
and the jevents.py one is. Having a common C file would defeat the
goal of hiding the API, but ultimately we'd need to get rid of it in
later changes when the empty/compressed implementations diverge.

Thanks,
Ian

> > +        int i;
> > +
> > +        /* on some platforms which uses cpus map, cpuid can be NULL for
> > +         * PMUs other than CORE PMUs.
> > +         */
> > +        if (!cpuid)
> > +                return NULL;
> > +
> > +        i = 0;
> > +        for (;;) {
> > +                const struct pmu_events_map *map = &pmu_events_map[i++];
> > +                if (!map->table)
> > +                        break;
> > +
> > +                if (!strcmp_cpuid_str(map->cpuid, cpuid)) {
> > +                        table = map->table;
> > +                        break;
> > +                }
> > +        }
> > +        free(cpuid);
> > +        return table;
> > +}