linux-kernel - Re: [RFC PATCH v1 02/37] libperf cpumap: improve max function

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Date:   Tue, 31 Aug 2021 16:16:57 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Riccardo Mancini <rickyman7@...il.com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [RFC PATCH v1 02/37] libperf cpumap: improve max function

Em Tue, Aug 31, 2021 at 03:47:10PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Sat, Aug 21, 2021 at 11:19:08AM +0200, Riccardo Mancini escreveu:
> > >From commit 7074674e7338863e ("perf cpumap: Maintain cpumaps ordered and
> > without dups"), perf_cpu_map elements are sorted in ascending order.
> > 
> > This patch improves the perf_cpu_map__max function by returning the last
> > element.
> > 
> > Signed-off-by: Riccardo Mancini <rickyman7@...il.com>
> > ---
> >  tools/lib/perf/cpumap.c | 12 ++++--------
> >  1 file changed, 4 insertions(+), 8 deletions(-)
> > 
> > diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> > index fb633272be3aaed9..80e03b2f0c60cce7 100644
> > --- a/tools/lib/perf/cpumap.c
> > +++ b/tools/lib/perf/cpumap.c
> > @@ -284,14 +284,10 @@ int perf_cpu_map__idx(struct perf_cpu_map *cpus, int cpu)
> >  
> >  int perf_cpu_map__max(struct perf_cpu_map *map)
> >  {
> > -	int i, max = -1;
> > -
> > -	for (i = 0; i < map->nr; i++) {
> > -		if (map->map[i] > max)
> > -			max = map->map[i];
> > -	}
> > -
> > -	return max;
> > +	if (map->nr > 0)
> > +		return map->map[map->nr-1];
> > +	else
> > +		return -1;
> 
> Applying, but adding spaces around the '-',

I ended up with this, ok?

+++ b/tools/lib/perf/cpumap.c
@@ -282,10 +282,8 @@ int perf_cpu_map__idx(struct perf_cpu_map *cpus, int cpu)

 int perf_cpu_map__max(struct perf_cpu_map *map)
 {
-       if (map->nr > 0)
-               return map->map[map->nr-1];
-       else
-               return -1;
+       // cpu_map__trim_new() qsort()s it, cpu_map__default_new() sorts it as well.
+       return map->nr > 0 ? map->map[map->nr - 1] : -1;
 }