linux-kernel - Re: [PATCH v3 3/5] perf c2c: Refactor display filter

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Date:   Wed, 13 Jan 2021 23:35:23 -0800
From:   Joe Perches <joe@...ches.com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Joe Mario <jmario@...hat.com>, David Ahern <dsahern@...il.com>,
        Don Zickus <dzickus@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/5] perf c2c: Refactor display filter

On Thu, 2021-01-14 at 11:39 +0800, Leo Yan wrote:
> When sort on the respective metrics (lcl_hitm, rmt_hitm, tot_hitm),
> macro FILTER_HITM is to filter out the cache line entries if its
> overhead is less than 1%.
> 
> This patch introduces static function filter_display() to replace macro;
> and refines its parameter with more flexbile way, rather than passing
> field name, it changes to pass the cache line's statistic value and the
> sum value.
[]
> diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
[]
> +static u8 filter_display(u32 val, u32 sum)
> +{
> +	double ld_dist;
> +
> +	if (sum) {
> +		ld_dist = ((double)(val) / (sum));
> +		if (ld_dist < DISPLAY_LINE_LIMIT)
> +			return HIST_FILTER__C2C;
> +	} else {
> +		return HIST_FILTER__C2C;
> +	}
> +
> +	return 0;
> +}

style:

It's generally better to test and return early and unindent the remainder.
Also, parentheses aren't necessary around now not-macro args.

{
	if (sum == 0 || ((double)val / sum) < DISPLAY_LINE_LIMIT)
		return HIST_FILTER__C2C;

	return 0;
}