netdev - Re: [PATCH v2 5/9] perf tools: avoid a malloc for array events

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Date:   Wed, 23 Oct 2019 10:58:30 +0200
From:   Jiri Olsa <jolsa@...hat.com>
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>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, clang-built-linux@...glegroups.com,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 5/9] perf tools: avoid a malloc for array events

On Tue, Oct 22, 2019 at 05:53:33PM -0700, Ian Rogers wrote:
> Use realloc rather than malloc+memcpy to possibly avoid a memory
> allocation when appending array elements.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka

> ---
>  tools/perf/util/parse-events.y | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
> index 26cb65798522..545ab7cefc20 100644
> --- a/tools/perf/util/parse-events.y
> +++ b/tools/perf/util/parse-events.y
> @@ -691,14 +691,12 @@ array_terms ',' array_term
>  	struct parse_events_array new_array;
>  
>  	new_array.nr_ranges = $1.nr_ranges + $3.nr_ranges;
> -	new_array.ranges = malloc(sizeof(new_array.ranges[0]) *
> -				  new_array.nr_ranges);
> +	new_array.ranges = realloc($1.ranges,
> +				sizeof(new_array.ranges[0]) *
> +				new_array.nr_ranges);
>  	ABORT_ON(!new_array.ranges);
> -	memcpy(&new_array.ranges[0], $1.ranges,
> -	       $1.nr_ranges * sizeof(new_array.ranges[0]));
>  	memcpy(&new_array.ranges[$1.nr_ranges], $3.ranges,
>  	       $3.nr_ranges * sizeof(new_array.ranges[0]));
> -	free($1.ranges);
>  	free($3.ranges);
>  	$$ = new_array;
>  }
> -- 
> 2.23.0.866.gb869b98d4c-goog
>