Re: [PATCH 09/18] perf metric: Collect referenced metrics in struct metric_ref_node

[Jiri Olsa <jolsa@redhat.com>]

On Tue, Jul 14, 2020 at 05:07:04PM -0700, Ian Rogers wrote:
> On Sun, Jul 12, 2020 at 6:27 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Collecting referenced metrics in struct metric_ref_node object,
> > so we can process them later on.
> >
> > The change will parse nested metric names out of expression and
> > 'resolve' them.
> >
> > All referenced metrics are dissolved into one context, meaning all
> > nested metrics events and added to the parent context.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/perf/util/metricgroup.c | 147 ++++++++++++++++++++++++++++++----
> >  1 file changed, 132 insertions(+), 15 deletions(-)
> >
> > diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> > index f0b0a053bfd2..9923eef1e2d4 100644
> > --- a/tools/perf/util/metricgroup.c
> > +++ b/tools/perf/util/metricgroup.c
> > @@ -102,12 +102,20 @@ void metricgroup__rblist_exit(struct rblist *metric_events)
> >         rblist__exit(metric_events);
> >  }
> >
> > +struct metric_ref_node {
> > +       const char *metric_name;
> > +       const char *metric_expr;
> > +       struct list_head list;
> > +};
> 
> Perhaps a comment like this above:
> /* A node in the list of referenced metrics. metric_expr is held as a
> convenience to avoid a search through the metric list. */

sounds good

> 
> > +
> >  struct egroup {
> >         struct list_head nd;
> >         struct expr_parse_ctx pctx;
> >         const char *metric_name;
> >         const char *metric_expr;
> >         const char *metric_unit;
> > +       struct list_head refs;
> > +       int refs_cnt;
> 
> A comment would be nice here as refs is a pretty overloaded term. For
> example, is refs_cnt a reference count for memory management or the
> length of the refs list? I'm unpopular and would use a long variable
> name here of something like referenced_metrics for the list.

how about metric_refs ? ;-)

> 
> >         int runtime;
> >         bool has_constraint;
> >  };
> > @@ -574,27 +582,66 @@ int __weak arch_get_runtimeparam(void)
> >  static int __add_metric(struct list_head *group_list,
> >                         struct pmu_event *pe,
> >                         bool metric_no_group,
> > -                       int runtime)
> > +                       int runtime,
> > +                       struct egroup **egp)
> 
> Rather than egp perhaps parent_eg or parent_metric?

I'm changing that later on, but perhaps not to parent_metric,
which sounds good, I'll check

> 
> >  {
> > +       struct metric_ref_node *ref;
> >         struct egroup *eg;
> >
> > -       eg = malloc(sizeof(*eg));
> > -       if (!eg)
> > -               return -ENOMEM;
> > +       if (*egp == NULL) {
> > +               /*
> > +                * We got in here for the master group,
> > +                * allocate it and put it on the list.
> > +                */
> > +               eg = malloc(sizeof(*eg));
> > +               if (!eg)
> > +                       return -ENOMEM;
> > +
> > +               expr__ctx_init(&eg->pctx);
> > +               eg->metric_name = pe->metric_name;
> > +               eg->metric_expr = pe->metric_expr;
> > +               eg->metric_unit = pe->unit;
> > +               eg->runtime = runtime;
> > +               eg->has_constraint = metric_no_group || metricgroup__has_constraint(pe);
> > +               INIT_LIST_HEAD(&eg->refs);
> > +               eg->refs_cnt = 0;
> > +               *egp = eg;
> > +       } else {
> > +               /*
> > +                * We got here for the referenced metric, via the
> > +                * recursive metricgroup__add_metric call, add
> > +                * it to the master group.
> 
> Probably want to avoid the term master here and below:
> https://www.kernel.org/doc/html/latest/process/coding-style.html?highlight=language%20master#naming
> Perhaps parent or referencing metric?

right.. will change

> 
> > +                */
> > +               eg = *egp;
> > +
> > +               ref = malloc(sizeof(*ref));
> > +               if (!ref)
> > +                       return -ENOMEM;
> >
> > -       expr__ctx_init(&eg->pctx);
> > -       eg->metric_name = pe->metric_name;
> > -       eg->metric_expr = pe->metric_expr;
> > -       eg->metric_unit = pe->unit;
> > -       eg->runtime = runtime;
> > -       eg->has_constraint = metric_no_group || metricgroup__has_constraint(pe);
> > +               ref->metric_name = pe->metric_name;
> > +               ref->metric_expr = pe->metric_expr;
> > +               list_add(&ref->list, &eg->refs);
> > +               eg->refs_cnt++;
> > +               eg->has_constraint |= metricgroup__has_constraint(pe);
> 
> Why not metric_no_group here? Perhaps use a function to avoid
> duplication with the code above.

oops, I think that has_constraint update should not be there at al,
just for the 'parent' metric, thanks!

> 
> > +       }
> >
> > +       /*
> > +        * For both the master and referenced metrics, we parse
> > +        * all the metric's IDs and add it to the parent context.
> > +        */
> >         if (expr__find_other(pe->metric_expr, NULL, &eg->pctx, runtime) < 0) {
> >                 expr__ctx_clear(&eg->pctx);
> >                 free(eg);
> >                 return -EINVAL;
> >         }
> >
> > +       /*
> > +        * We add new group only in the 'master' call,
> > +        * so bail out for referenced metric case.
> > +        */
> > +       if (eg->refs_cnt)
> > +               return 0;
> > +
> >         if (list_empty(group_list))
> >                 list_add(&eg->nd, group_list);
> >         else {
> > @@ -636,14 +683,63 @@ static struct pmu_event *find_metric(const char *metric, struct pmu_events_map *
> >
> >  static int add_metric(struct list_head *group_list,
> >                       struct pmu_event *pe,
> > -                     bool metric_no_group)
> > +                     bool metric_no_group,
> > +                     struct egroup **egp);
> > +
> > +static int resolve_metric(struct egroup *eg,
> > +                         bool metric_no_group,
> > +                         struct list_head *group_list,
> > +                         struct pmu_events_map *map)
> > +{
> > +       struct hashmap_entry *cur;
> > +       size_t bkt;
> > +       bool all;
> > +       int ret;
> > +
> > +       /*
> > +        * Iterate all the parsed IDs and if there's metric,
> > +        * add it to the context.
> > +        */
> 
> Does this mean that the ID doesn't need to begin "metric:" to
> reference a different metric as per Andi Kleen's request?

correct, that's why I separated find_metric function earlier,
now I see I did not put this to the changelog :-\ sry

> 
> > +       do {
> > +               all = true;
> > +               hashmap__for_each_entry((&eg->pctx.ids), cur, bkt) {
> > +                       struct pmu_event *pe;
> > +
> > +                       pe = find_metric(cur->key, map);
> > +                       if (!pe)
> > +                               continue;
> > +
> > +                       all = false;
> > +                       /* The metric key itself needs to go out.. */
> > +                       expr__del_id(&eg->pctx, cur->key);
> > +
> > +                       /* ... and it gets resolved to the parent context. */
> > +                       ret = add_metric(group_list, pe, metric_no_group, &eg);
> > +                       if (ret)
> > +                               return ret;
> > +
> > +                       /*
> > +                        * We added new metric to hashmap, so we need
> > +                        * to break the iteration and start over.
> > +                        */
> > +                       break;
> > +               }
> > +       } while (!all);
> > +
> > +       return 0;
> > +}

SNIP