Re: [RFC v1 05/16] perf kwork: Overwrite original atom in the list when a new atom is pushed.

[Yang Jihong]

Hello,

On 2023/9/4 12:13, Ian Rogers wrote:
> On Sat, Aug 12, 2023 at 1:52 AM Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
> > work_push_atom() supports nesting. Currently, all supported kworks are not
> > nested. A `overwrite` parameter is added to overwrite the original atom in
> > the list.
> >
> > Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
> > ---
> >   tools/perf/builtin-kwork.c | 24 ++++++++++++++++++------
> >   1 file changed, 18 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/perf/builtin-kwork.c b/tools/perf/builtin-kwork.c
> > index 42ea59a957ae..f620911a26a2 100644
> > --- a/tools/perf/builtin-kwork.c
> > +++ b/tools/perf/builtin-kwork.c
> > @@ -392,9 +392,10 @@ static int work_push_atom(struct perf_kwork *kwork,
> >                            struct evsel *evsel,
> >                            struct perf_sample *sample,
> >                            struct machine *machine,
> > -                         struct kwork_work **ret_work)
> > +                         struct kwork_work **ret_work,
> > +                         bool overwrite)
>
> kerneldoc would be useful. Pushing something seems self-evident but
> what does overwrite mean without reading the code?

Okay, I'll add comments.

> >   {
> > -       struct kwork_atom *atom, *dst_atom;
> > +       struct kwork_atom *atom, *dst_atom, *last_atom;
> >          struct kwork_work *work, key;
> >
> >          BUG_ON(class->work_init == NULL);
> > @@ -427,6 +428,17 @@ static int work_push_atom(struct perf_kwork *kwork,
> >          if (ret_work != NULL)
> >                  *ret_work = work;
> >
> > +       if (overwrite) {
> > +               last_atom = list_last_entry_or_null(&work->atom_list[src_type],
> > +                                                   struct kwork_atom, list);
> > +               if (last_atom) {
> > +                       atom_del(last_atom);
> > +
> > +                       kwork->nr_skipped_events[src_type]++;
> > +                       kwork->nr_skipped_events[KWORK_TRACE_MAX]++;
> > +               }
> > +       }
> > +
> >          list_add_tail(&atom->list, &work->atom_list[src_type]);
> >
> >          return 0;
> > @@ -502,7 +514,7 @@ static int report_entry_event(struct perf_kwork *kwork,
> >   {
> >          return work_push_atom(kwork, class, KWORK_TRACE_ENTRY,
> >                                KWORK_TRACE_MAX, evsel, sample,
> > -                             machine, NULL);
> > +                             machine, NULL, true);
>
> nit: for constant arguments it can be useful to add parameter names
> which can enable checks like clang-tidy's bugprone argument:
> https://clang.llvm.org/extra/clang-tidy/checks/bugprone/argument-comment.html
> This would make this:
>          return work_push_atom(kwork, class, KWORK_TRACE_ENTRY,
>                                KWORK_TRACE_MAX, evsel, sample,
>                                machine, /*ret_work=*/NULL, /*overwite=*/true);
Thanks for your advice, will add parameter names later.

Thanks,
Yang