linux-kernel - Re: [PATCH v5 19/50] perf maps: Do simple merge if given map doesn't overlap

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Date:   Mon, 4 Dec 2023 16:06:34 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Nick Terrell <terrelln@...com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        "Steinar H. Gunderson" <sesse@...gle.com>,
        Liam Howlett <liam.howlett@...cle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Colin Ian King <colin.i.king@...il.com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Ming Wang <wangming01@...ngson.cn>,
        James Clark <james.clark@....com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Leo Yan <leo.yan@...aro.org>,
        Ravi Bangoria <ravi.bangoria@....com>,
        German Gomez <german.gomez@....com>,
        Changbin Du <changbin.du@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>, Li Dong <lidong@...o.com>,
        Sandipan Das <sandipan.das@....com>,
        liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Guilherme Amadio <amadio@...too.org>
Subject: Re: [PATCH v5 19/50] perf maps: Do simple merge if given map doesn't overlap

On Mon, Nov 27, 2023 at 2:10 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Simplify merge in for the simple case of a non-overlapping map.
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

A nitpick below.

> ---
>  tools/perf/util/maps.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
> index 40df08dd9bf3..14e1a169433d 100644
> --- a/tools/perf/util/maps.c
> +++ b/tools/perf/util/maps.c
> @@ -696,9 +696,20 @@ void maps__fixup_end(struct maps *maps)
>  int maps__merge_in(struct maps *kmaps, struct map *new_map)
>  {
>         struct map_rb_node *rb_node;
> +       struct rb_node *first;
> +       bool overlaps;
>         LIST_HEAD(merged);
>         int err = 0;
>
> +       down_read(maps__lock(kmaps));
> +       first = first_ending_after(kmaps, new_map);
> +       overlaps = first &&
> +               map__start(rb_entry(first, struct map_rb_node, rb_node)->map) < map__end(new_map);

Can you please break this like below?

    rb_node = first ? rb_entry(first, struct map_rb_node, rb_node) : NULL;
    overlap = rb_node && map__start(rb_node->map) < map_end(new_map);

Thanks,
Namhyung


> +       up_read(maps__lock(kmaps));
> +
> +       if (!overlaps)
> +               return maps__insert(kmaps, new_map);
> +
>         maps__for_each_entry(kmaps, rb_node) {
>                 struct map *old_map = rb_node->map;
>
> --
> 2.43.0.rc1.413.gea7ed67945-goog
>