linux-kernel - Re: [PATCH v3 1/3] perf report: Change sort order by a specified event in group

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Date:   Mon, 16 Dec 2019 08:31:13 +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 v3 1/3] perf report: Change sort order by a specified
 event in group

On Thu, Dec 12, 2019 at 08:33:35PM +0800, Jin Yao wrote:

SNIP

> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/Documentation/perf-report.txt |   4 +
>  tools/perf/builtin-report.c              |  10 +++
>  tools/perf/ui/hist.c                     | 108 +++++++++++++++++++----
>  tools/perf/util/symbol_conf.h            |   1 +
>  4 files changed, 108 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
> index 8dbe2119686a..9ade613ef020 100644
> --- a/tools/perf/Documentation/perf-report.txt
> +++ b/tools/perf/Documentation/perf-report.txt
> @@ -371,6 +371,10 @@ OPTIONS
>  	Show event group information together. It forces group output also
>  	if there are no groups defined in data file.
>  
> +--group-sort-idx::
> +	Sort the output by the event at the index n in group. If n is invalid,
> +	sort by the first event. WARNING: This should be used with --group.

--group in record or report?

you can also create groups with -e '{}', not just --group option

I wonder you could check early on 'evlist->nr_groups' and fail
if there's no group defined if the option is enabled

also what happens when we have more groups?

I think the option is easy to use as it is, just needs to be explained
consequences for more groups with different amount of events

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;
> +	}
> +
> +	if (idx >= 1 && idx < nr_members) {

do we need to continue here if idx is out of the limit?
I'm not sure but mybe in that case the comparison above
should be enough?

thanks,
jirka