Re: [PATCH v2 2/3] perf pmus: Add scan that ignores duplicates, use for perf list

From: Ian Rogers
Date: Mon Aug 14 2023 - 11:59:04 EST

On Fri, Aug 11, 2023 at 8:51 AM John Garry <john.g.garry@xxxxxxxxxx> wrote:
>
> On 10/08/2023 22:49, Ian Rogers wrote:
> > When there are multiple PMUs that differ only by suffix, by default
> > just list the first one and skip all others. As the PMUs are sorted,
> > the scan routine checks that the PMU names match and the numbers are
> > consecutive. If "-v" is passed to "perf list" then list all PMUs.
>
> I really think that this should be merged with the next change. I don't
> like the intermediate step of by default only printing the first PMU.

Ack. I'll leave it as 3 patches and then leave it to Arnaldo squash as
quite often he wants more patches.

> >
> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> > tools/perf/builtin-list.c | 8 +++++
> > tools/perf/util/pmus.c | 54 ++++++++++++++++++++++++++++++++--
> > tools/perf/util/print-events.h | 1 +
> > 3 files changed, 61 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
> > index 7fec2cca759f..8fe4ddf02c14 100644
> > --- a/tools/perf/builtin-list.c
> > +++ b/tools/perf/builtin-list.c
> > @@ -423,6 +423,13 @@ static void json_print_metric(void *ps __maybe_unused, const char *group,
> > strbuf_release(&buf);
> > }
> >
> > +static bool default_skip_duplicate_pmus(void *ps)
> > +{
> > + struct print_state *print_state = ps;
> > +
> > + return !print_state->long_desc;
> > +}
> > +
> > int cmd_list(int argc, const char **argv)
> > {
> > int i, ret = 0;
> > @@ -434,6 +441,7 @@ int cmd_list(int argc, const char **argv)
> > .print_end = default_print_end,
> > .print_event = default_print_event,
> > .print_metric = default_print_metric,
> > + .skip_duplicate_pmus = default_skip_duplicate_pmus,
> > };
> > const char *cputype = NULL;
> > const char *unit_name = NULL;
> > diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
> > index 3581710667b0..5073843aca19 100644
> > --- a/tools/perf/util/pmus.c
> > +++ b/tools/perf/util/pmus.c
> > @@ -275,6 +275,50 @@ struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu)
> > return NULL;
> > }
> >
> > +static struct perf_pmu *perf_pmus__scan_skip_duplicates(struct perf_pmu *pmu)
> > +{
> > + bool use_core_pmus = !pmu || pmu->is_core;
> > + int last_pmu_name_len = 0;
> > + unsigned long last_pmu_num = 0;
> > + const char *last_pmu_name = (pmu && pmu->name) ? pmu->name : "";
> > +
> > + if (!pmu) {
> > + pmu_read_sysfs(/*core_only=*/false);
> > + pmu = list_prepare_entry(pmu, &core_pmus, list);
> > + } else
> > + last_pmu_name_len = pmu_name_len_no_suffix(pmu->name ?: "", &last_pmu_num);
> > +
> > + if (use_core_pmus) {
> > + list_for_each_entry_continue(pmu, &core_pmus, list) {
> > + unsigned long pmu_num = 0;
> > + int pmu_name_len = pmu_name_len_no_suffix(pmu->name ?: "", &pmu_num);
> > +
> > + if (last_pmu_name_len == pmu_name_len &&
> > + (last_pmu_num + 1 == pmu_num) &&
> > + !strncmp(last_pmu_name, pmu->name ?: "", pmu_name_len)) {
> > + last_pmu_num++;
> > + continue;
> > + }
> > + return pmu;
> > + }
> > + pmu = NULL;
>
> you assign pmu NULL
>
> > + pmu = list_prepare_entry(pmu, &other_pmus, list);
>
> and then re-assign it. If list_prepare_entry() needs first arg = NULL,
> then can just use NULL explicitly?

Done.

> > + }
> > + list_for_each_entry_continue(pmu, &other_pmus, list) {
> > + unsigned long pmu_num = 0;
> > + int pmu_name_len = pmu_name_len_no_suffix(pmu->name ?: "", &pmu_num);
> > +
> > + if (last_pmu_name_len == pmu_name_len &&
> > + (last_pmu_num + 1 == pmu_num) &&
> > + !strncmp(last_pmu_name, pmu->name ?: "", pmu_name_len)) {
> > + last_pmu_num++;
> > + continue;
>
> Can some of this code be factored out from the previous patch? It's
> doing something similar, right?

The previous patch implemented list sorting and a list comparator
whilst this patch is skipping PMUs if they follow the pattern:
uncore_xyz_0
uncore_xyz_1 <- skip
uncore_xyz_2 <- skip
The pmu_name_len_no_suffix is factored out and shared between both
routines. The comparator doesn't maintain state whilst this code does.
So I don't see a way to refactor things further.

Thanks,
Ian

> > + }
> > + return pmu;
> > + }
> > + return NULL;
> > +}
> > +
> > const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str)
> > {
> > struct perf_pmu *pmu = NULL;
> > @@ -429,10 +473,16 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
> > int printed = 0;
> > int len, j;
> > struct sevent *aliases;
> > + struct perf_pmu *(*scan_fn)(struct perf_pmu *);
> > +
> > + if (print_cb->skip_duplicate_pmus(print_state))
> > + scan_fn = perf_pmus__scan_skip_duplicates;
> > + else
> > + scan_fn = perf_pmus__scan;
> >
> > pmu = NULL;
> > len = 0;
> > - while ((pmu = perf_pmus__scan(pmu)) != NULL) {
> > + while ((pmu = scan_fn(pmu)) != NULL) {
> > list_for_each_entry(event, &pmu->aliases, list)
> > len++;
> > if (pmu->selectable)
> > @@ -445,7 +495,7 @@ void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *p
> > }
> > pmu = NULL;
> > j = 0;
> > - while ((pmu = perf_pmus__scan(pmu)) != NULL) {
> > + while ((pmu = scan_fn(pmu)) != NULL) {
> > bool is_cpu = pmu->is_core;
> >
> > list_for_each_entry(event, &pmu->aliases, list) {
> > diff --git a/tools/perf/util/print-events.h b/tools/perf/util/print-events.h
> > index d7fab411e75c..bf4290bef0cd 100644
> > --- a/tools/perf/util/print-events.h
> > +++ b/tools/perf/util/print-events.h
> > @@ -26,6 +26,7 @@ struct print_callbacks {
> > const char *expr,
> > const char *threshold,
> > const char *unit);
> > + bool (*skip_duplicate_pmus)(void *print_state);
> > };
> >
> > /** Print all events, the default when no options are specified. */
>