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 13:14:53 +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 08:01:44PM +0800, Jin, Yao wrote:
> 
> 
> On 12/11/2019 7:38 PM, Jiri Olsa wrote:
> > 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
> > 
> 
> Hi,
> 
> I think we may continue comparing the remaining of fields if the index field
> is equal. :)

aah, I missed it's actualy == used in the first one ;-)

why don't you just call it directly?

	ret = field_cmp(fields_a[idx], fields_b[idx])
	if (ret)
		goto out;

jirka