linux-kernel - Re: [PATCH 02/13 v4] perf tools: Use allocator for perf_cpu

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Date:   Sun, 15 Nov 2020 22:17:32 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     James Clark <james.clark@....com>
Cc:     linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        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>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        John Garry <john.garry@...wei.com>
Subject: Re: [PATCH 02/13 v4] perf tools: Use allocator for perf_cpu_map

On Fri, Nov 13, 2020 at 07:26:43PM +0200, James Clark wrote:
> Use the existing allocator for perf_cpu_map to avoid use
> of raw malloc. This could cause an issue in later commits
> where the size of perf_cpu_map is changed.
> 
> No functional changes.
> 
> Signed-off-by: James Clark <james.clark@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Thomas Richter <tmricht@...ux.ibm.com>
> Cc: John Garry <john.garry@...wei.com>
> ---
>  tools/perf/util/cpumap.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> index dc5c5e6fc502..fd7d0a77a9e6 100644
> --- a/tools/perf/util/cpumap.c
> +++ b/tools/perf/util/cpumap.c
> @@ -132,15 +132,16 @@ int cpu_map__build_map(struct perf_cpu_map *cpus, struct perf_cpu_map **res,
>  		       int (*f)(struct perf_cpu_map *map, int cpu, void *data),
>  		       void *data)
>  {
> -	struct perf_cpu_map *c;
>  	int nr = cpus->nr;
> +	struct perf_cpu_map *c = perf_cpu_map__empty_new(nr);
>  	int cpu, s1, s2;
>  
> -	/* allocate as much as possible */
> -	c = calloc(1, sizeof(*c) + nr * sizeof(int));
>  	if (!c)
>  		return -1;
>  
> +	/* Reset size as it may only be partially filled */
> +	c->nr = 0;
> +
>  	for (cpu = 0; cpu < nr; cpu++) {
>  		s1 = f(cpus, cpu, data);
>  		for (s2 = 0; s2 < c->nr; s2++) {

also remove refcount_set call down here,
it's already in set in perf_cpu_map__empty_new

thanks,
jirka

> -- 
> 2.28.0
>