linux-kernel - Re: [PATCH v2 1/3] perf report: Change sort order by a specified event in group

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Date:   Wed, 11 Dec 2019 12:38:15 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v2 1/3] perf report: Change sort order by a specified
 event in group

On Wed, Dec 11, 2019 at 03:30:34PM +0800, Jin Yao wrote:

SNIP

> +
> +static int __hpp__group_sort_idx(struct hist_entry *a, struct hist_entry *b,
> +				 hpp_field_fn get_field, int idx)
> +{
> +	struct evsel *evsel = hists_to_evsel(a->hists);
> +	u64 *fields_a, *fields_b;
> +	int cmp, nr_members, ret, i;
> +
> +	cmp = field_cmp(get_field(a), get_field(b));
> +	if (!perf_evsel__is_group_event(evsel))
> +		return cmp;
> +
> +	nr_members = evsel->core.nr_members;
> +	ret = pair_fields_alloc(a, b, get_field, nr_members,
> +			      &fields_a, &fields_b);
> +	if (ret) {
> +		ret = cmp;
> +		goto out;
> +	}
> +
> +	for (i = 1; i < nr_members; i++) {
> +		if (i == idx) {
> +			ret = field_cmp(fields_a[i], fields_b[i]);
> +			if (ret)
> +				goto out;
> +		}
> +	}
> +
> +	if (cmp) {
> +		ret = cmp;
> +		goto out;
> +	}
> +
> +	for (i = 1; i < nr_members; i++) {
> +		if (i != idx) {
> +			ret = field_cmp(fields_a[i], fields_b[i]);
> +			if (ret)
> +				goto out;
> +		}

hi,
I'm missing why we compare the fields for 2nd time in here

thanks,
jirka