Re: [RFC PATCH v3 07/18] perf stat: Add functions to set counter bitmaps for hardware-grouping method

[Ian Rogers]

On Tue, Dec 12, 2023 at 3:03 PM <weilin.wang@xxxxxxxxx> wrote:
>
> From: Weilin Wang <weilin.wang@xxxxxxxxx>
>
> Add metricgroup__event_info data structure to represent an event in the
> metric grouping context; the list of counters and the PMU name an event
> should be collected with.
>
> Add functions to parse event counter info from pmu-events and generate a
> list of metricgroup__event_info data to prepare grouping.
>
> Signed-off-by: Weilin Wang <weilin.wang@xxxxxxxxx>
> ---
>  tools/perf/util/metricgroup.c | 196 +++++++++++++++++++++++++++++++++-
>  tools/perf/util/metricgroup.h |  27 +++++
>  2 files changed, 220 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 8d1143ee898c..24268882d355 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -1432,6 +1432,182 @@ static int build_combined_expr_ctx(const struct list_head *metric_list,
>         return ret;
>  }
>
> +/**
> + * set_counter_bitmap - The counter bit mapping: [8-15,0-7], e.g. the GP0 is the
> + * 8th bit and GP7 is the 1st bit in this 16-bits bitmap. It is helpful for
> + * assigning GP4-7 before GP0-3 because some events can be collected using GP0-3
> + * only on some platforms.
> + */
> +static int set_counter_bitmap(int pos, unsigned long *bitmap)
> +{
> +       if (pos >= NR_COUNTERS || pos < 0)
> +               return -EINVAL;
> +       if (pos <= 7)
> +               pos = TRANSFER_FIRST_BYTE(pos);
> +       else
> +               pos = TRANSFER_SEC_BYTE(pos);
> +       *bitmap |= 1ul << pos;

__set_bit may be more canonical here, in case we ever had more than 64 counters.

> +       return 0;
> +}
> +
> +static int parse_fixed_counter(const char *counter,
> +                             unsigned long *bitmap,
> +                             bool *fixed)
> +{
> +       int ret = -ENOENT;
> +       //TODO: this pattern is different on some other platforms
> +       const char *pattern = "Fixed counter ";
> +       int pos = 0;
> +
> +       if (!strncmp(counter, pattern, strlen(pattern))) {
> +               pos = atoi(counter + strlen(pattern));
> +               ret = set_counter_bitmap(pos, bitmap);
> +               if (ret)
> +                       return ret;
> +               *fixed = true;
> +               return 0;
> +       }
> +       return ret;
> +}

It'd be nice if the counter APIs that are specific to a PMU could be
part of the struct pmu API.

> +
> +/**
> + * parse_counter - Parse event counter info from pmu-events and set up bitmap
> + * accordingly.
> + *
> + * @counter: counter info string to be parsed.
> + * @bitmap: bitmap to set based on counter info parsed.
> + * @fixed: is set to true if the event uses fixed counter.
> + */
> +static int parse_counter(const char *counter,
> +                       unsigned long *bitmap,
> +                       bool *fixed)
> +{
> +       int ret = 0;
> +       char *p;
> +       char *tok;
> +       int pos = 0;
> +
> +       ret = parse_fixed_counter(counter, bitmap, fixed);
> +       // ret==0 means matched with fixed counter
> +       if (ret == 0)
> +               return ret;
> +
> +       p = strdup(counter);
> +       tok = strtok(p, ",");
> +       if (!tok)
> +               return -ENOENT;
> +
> +       while (tok) {
> +               pos = atoi(tok);
> +               ret = set_counter_bitmap(pos, bitmap);
> +               if (ret)
> +                       return ret;
> +               tok = strtok(NULL, ",");
> +       }
> +       return 0;
> +}
> +
> +static struct metricgroup__event_info *event_info__new(const char *name,
> +                                                     const char *pmu_name,
> +                                                     const char *counter,
> +                                                     bool free_counter)
> +{
> +       int ret = 0;
> +       char *bit_buf = malloc(NR_COUNTERS);
> +       bool fixed_counter = false;
> +       struct metricgroup__event_info *e;
> +
> +       e = zalloc(sizeof(*e));
> +       if (!e)
> +               return NULL;
> +       if (!pmu_name)
> +               pmu_name = "core";
> +
> +       e->name = name;
> +       e->free_counter = free_counter;
> +       e->pmu_name = strdup(pmu_name);
> +       if (free_counter) {
> +               ret = set_counter_bitmap(0, e->counters);
> +               if (ret)
> +                       return NULL;
> +       } else {
> +               ret = parse_counter(counter, e->counters, &fixed_counter);
> +               if (ret)
> +                       return NULL;
> +               e->fixed_counter = fixed_counter;
> +       }
> +
> +       bitmap_scnprintf(e->counters, NR_COUNTERS, bit_buf, NR_COUNTERS);
> +       pr_debug("Event %s requires pmu %s counter: %s bitmap %s, [pmu=%s]\n",
> +               e->name, e->pmu_name, counter, bit_buf, pmu_name);
> +
> +       return e;
> +}
> +
> +struct metricgroup__add_metric_event_data {
> +       struct list_head *list;
> +       /* pure event name, exclude umask and other info*/
> +       const char *event_name;
> +       /* event name and umask if applicable*/
> +       const char *event_id;
> +};
> +
> +static int metricgroup__add_metric_event_callback(const struct pmu_event *pe,
> +                                                const struct pmu_events_table *table __maybe_unused,
> +                                                void *data)
> +{
> +       struct metricgroup__event_info *event;
> +       struct metricgroup__add_metric_event_data *d = data;
> +
> +       if (!strcasecmp(pe->name, d->event_name)) {
> +               event = event_info__new(d->event_id, pe->pmu, pe->counter, /*free_counter=*/false);
> +               if (!event)
> +                       return -ENOMEM;
> +               list_add(&event->nd, d->list);
> +       }
> +
> +       return 0;
> +}
> +
> +/**
> + * get_metricgroup_events - Find counter requirement of events from the
> + * pmu_events table
> + * @full_id: the full event identifiers.
> + * @table: pmu_events table that is searched for event data.
> + * @event_info_list: the list that the new event counter info added to.
> + */
> +static int get_metricgroup_events(const char *full_id,
> +                                const struct pmu_events_table *table,
> +                                struct list_head *event_info_list)
> +{
> +       LIST_HEAD(list);
> +       int ret = 0;
> +       const char *id;
> +       const char *rsep, *sep = strchr(full_id, '@');
> +
> +       if (sep) {
> +               rsep = strchr(full_id, ',');
> +               id = strndup(sep + 1, rsep - sep - 1);
> +               if (ret)
> +                       goto out;
> +       } else {
> +               id = full_id;
> +       }
> +       {
> +               struct metricgroup__add_metric_event_data data = {
> +                       .list = &list,
> +                       .event_name = id,
> +                       .event_id = full_id,
> +               };
> +               ret = pmu_events_table_for_each_event(table,
> +                               metricgroup__add_metric_event_callback, &data);
> +       }
> +
> +out:
> +       list_splice(&list, event_info_list);
> +       return ret;
> +}
> +
>  /**
>   * hw_aware_build_grouping - Build event groupings by reading counter
>   * requirement of the events and counter available on the system from
> @@ -1445,9 +1621,25 @@ static int hw_aware_build_grouping(struct expr_parse_ctx *ctx __maybe_unused,
>                                   const char *modifier __maybe_unused)
>  {
>         int ret = 0;
> +       struct hashmap_entry *cur;
> +       LIST_HEAD(pmu_info_list);
> +       LIST_HEAD(event_info_list);
> +       size_t bkt;
> +       const struct pmu_events_table *etable = perf_pmu__find_events_table(NULL);
> +
> +#define RETURN_IF_NON_ZERO(x) do { if (x) return x; } while (0)
> +       hashmap__for_each_entry(ctx->ids, cur, bkt) {
> +               const char *id = cur->pkey;
> +
> +               pr_debug("found event %s\n", id);
> +
> +               ret = get_metricgroup_events(id, etable, &event_info_list);
> +               if (ret)
> +                       return ret;
> +       }
>
> -       pr_debug("This is a placeholder\n");
>         return ret;
> +#undef RETURN_IF_NON_ZERO
>  }
>
>  static void group_str_free(struct metricgroup__group_strs *g)
> @@ -1521,8 +1713,6 @@ static int hw_aware_parse_ids(struct perf_pmu *fake_pmu,
>         *out_evlist = parsed_evlist;
>         parsed_evlist = NULL;
>  err_out:
> -       parse_events_error__exit(&parse_error);
> -       evlist__delete(parsed_evlist);
>         metricgroup__free_grouping_strs(&groupings);
>         return ret;
>  }
> diff --git a/tools/perf/util/metricgroup.h b/tools/perf/util/metricgroup.h
> index 89809df85644..3704545c9a11 100644
> --- a/tools/perf/util/metricgroup.h
> +++ b/tools/perf/util/metricgroup.h
> @@ -5,6 +5,7 @@
>  #include <linux/list.h>
>  #include <linux/rbtree.h>
>  #include <stdbool.h>
> +#include <linux/bitmap.h>
>  #include "pmu-events/pmu-events.h"
>  #include "strbuf.h"
>
> @@ -67,6 +68,32 @@ struct metric_expr {
>         int runtime;
>  };
>

If this is just used in metricgroup.c then it'd be better to keep the
definitions there for the sake of encapsulation.

> +/* Maximum number of counters per PMU*/
> +#define NR_COUNTERS    16

Fixed and/or generic?

> +/*
> + * Transfer bit position in the bitmap to ensure start assigning counter from
> + * the last GP counter to the first.
> + * bit15 <---> bit0
> + * [GP8-GP15] [GP0-GP7]
> + */
> +#define TRANSFER_FIRST_BYTE(pos) (7 - pos)
> +#define TRANSFER_SEC_BYTE(pos) (23 - pos)

Not sure why this bit flipping is necessary, if fixed counters are
separated out to their own bitmap does it help?

> +
> +/**
> + * An event used in a metric. This info is for metric grouping.
> + */
> +struct metricgroup__event_info {
> +       struct list_head nd;
> +       /** The name of the event. */
> +       const char *name;
> +       /** The name of the pmu the event be collected on. */
> +       const char *pmu_name;

Could we use the "struct pmu*" here?

> +       bool fixed_counter;
> +       bool free_counter;

Missing comment for *_counter.

Thanks,
Ian

> +       /** The counters the event allowed to be collected on. */
> +       DECLARE_BITMAP(counters, NR_COUNTERS);
> +};
> +
>  /**
>   * Each group is one node in the group string list.
>   */
> --
> 2.39.3
>