linux-kernel - Re: [PATCH v2] perf parse-events: Make X modifier more respectful of groups

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Message-ID: <86dc089a-1a0d-48e5-9aaa-5ae0ddf22a7c@linux.intel.com>
Date: Mon, 20 Oct 2025 11:00:28 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Ian Rogers <irogers@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
 Thomas Falcon <thomas.falcon@...el.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf parse-events: Make X modifier more respectful of
 groups


On 10/18/2025 7:03 AM, Ian Rogers wrote:
> Events with an X modifier were reordered within a group, for example
> slots was made the leader in:
> ```
> $ perf record -e '{cpu/mem-stores/ppu,cpu/slots/uX}' -- sleep 1
> ```
>
> Fix by making `dont_regroup` evsels always use their index for
> sorting. Make the cur_leader, when fixing the groups, be that of
> `dont_regroup` evsel so that the `dont_regroup` evsel doesn't become a
> leader.
>
> On a tigerlake this patch corrects this and meets expectations in:
> ```
> $ perf stat -e '{cpu/mem-stores/,cpu/slots/uX}' -a -- sleep 0.1
>
>  Performance counter stats for 'system wide':
>
>         83,458,652      cpu/mem-stores/
>      2,720,854,880      cpu/slots/uX
>
>        0.103780587 seconds time elapsed
>
> $ perf stat -e 'slots,slots:X' -a -- sleep 0.1
>
>  Performance counter stats for 'system wide':
>
>        732,042,247      slots                (48.96%)
>        643,288,155      slots:X              (51.04%)
>
>        0.102731018 seconds time elapsed
> ```
>
> Closes: https://lore.kernel.org/lkml/18f20d38-070c-4e17-bc90-cf7102e1e53d@linux.intel.com/
> Fixes: 035c17893082 ("perf parse-events: Add 'X' modifier to exclude an event from being regrouped")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/parse-events.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 3aec86aebdc6..0c0dc20b1c13 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -1973,14 +1973,18 @@ static int evlist__cmp(void *_fg_idx, const struct list_head *l, const struct li
>  	 * event's index is used. An index may be forced for events that
>  	 * must be in the same group, namely Intel topdown events.
>  	 */
> -	if (*force_grouped_idx != -1 && arch_evsel__must_be_in_group(lhs)) {
> +	if (lhs->dont_regroup) {
> +		lhs_sort_idx = lhs_core->idx;
> +	} else if (*force_grouped_idx != -1 && arch_evsel__must_be_in_group(lhs)) {
>  		lhs_sort_idx = *force_grouped_idx;
>  	} else {
>  		bool lhs_has_group = lhs_core->leader != lhs_core || lhs_core->nr_members > 1;
>  
>  		lhs_sort_idx = lhs_has_group ? lhs_core->leader->idx : lhs_core->idx;
>  	}
> -	if (*force_grouped_idx != -1 && arch_evsel__must_be_in_group(rhs)) {
> +	if (rhs->dont_regroup) {
> +		rhs_sort_idx = rhs_core->idx;
> +	} else if (*force_grouped_idx != -1 && arch_evsel__must_be_in_group(rhs)) {
>  		rhs_sort_idx = *force_grouped_idx;
>  	} else {
>  		bool rhs_has_group = rhs_core->leader != rhs_core || rhs_core->nr_members > 1;
> @@ -2078,10 +2082,10 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
>  	 */
>  	idx = 0;
>  	list_for_each_entry(pos, list, core.node) {
> -		const struct evsel *pos_leader = evsel__leader(pos);
> +		struct evsel *pos_leader = evsel__leader(pos);
>  		const char *pos_pmu_name = pos->group_pmu_name;
>  		const char *cur_leader_pmu_name;
> -		bool pos_force_grouped = force_grouped_idx != -1 &&
> +		bool pos_force_grouped = force_grouped_idx != -1 && !pos->dont_regroup &&
>  			arch_evsel__must_be_in_group(pos);
>  
>  		/* Reset index and nr_members. */
> @@ -2095,8 +2099,8 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
>  		 * groups can't span PMUs.
>  		 */
>  		if (!cur_leader || pos->dont_regroup) {
> -			cur_leader = pos;
> -			cur_leaders_grp = &pos->core;
> +			cur_leader = pos->dont_regroup ? pos_leader : pos;
> +			cur_leaders_grp = &cur_leader->core;
>  			if (pos_force_grouped)
>  				force_grouped_leader = pos;
>  		}

LGTM. Reviewed-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>

Thanks for fixing this issue so quickly.