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Message-ID: <CAP-5=fUi+oF8kzjYguDz6yjLVL-crFKrLGw7=3jgUeFik_p-_g@mail.gmail.com>
Date: Fri, 17 Oct 2025 14:53:25 -0700
From: Ian Rogers <irogers@...gle.com>
To: "Falcon, Thomas" <thomas.falcon@...el.com>
Cc: "alexander.shishkin@...ux.intel.com" <alexander.shishkin@...ux.intel.com>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>, "acme@...nel.org" <acme@...nel.org>,
"mingo@...hat.com" <mingo@...hat.com>, "Hunter, Adrian" <adrian.hunter@...el.com>,
"namhyung@...nel.org" <namhyung@...nel.org>, "jolsa@...nel.org" <jolsa@...nel.org>,
"dapeng1.mi@...ux.intel.com" <dapeng1.mi@...ux.intel.com>
Subject: Re: [PATCH v1] perf parse-events: Make X modifier more respectful of groups
On Fri, Oct 17, 2025 at 10:55 AM Falcon, Thomas <thomas.falcon@...el.com> wrote:
>
> On Fri, 2025-10-17 at 09:57 -0700, 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
> > ```
> >
>
> Hi Ian, just confirming the results on an Alder Lake:
>
> % sudo ./perf stat -e '{cpu_core/mem-stores/,cpu_core/slots/uX}' -a --
> sleep 0.1
>
> Performance counter stats for 'system wide':
>
> 23,097,346 cpu_core/mem-stores/
> 666,910,974 cpu_core/slots/uX
>
> 0.101369982 seconds time elapsed
>
> % sudo ./perf stat -e 'slots,slots:X' -a -- sleep 0.1
>
> Performance counter stats for 'system wide':
>
> 1,775,555,180 cpu_core/slots/
> (50.08%)
> 1,910,073,872 cpu_core/slots/X
> (49.92%)
>
> 0.101368283 seconds time elapsed
>
> Tested-by: Thomas Falcon <thomas.falcon@...el.com>
I found an issue when the slots event is injected and will look at it in v2:
```
$ perf stat -v -e 'topdown-retiring' -a -- sleep 0.1
Using CPUID GenuineIntel-6-8D-1
topdown-retiring -> cpu/topdown-retiring/
WARNING: events were regrouped to match PMUs
evlist after sorting/fixing: '{slots,topdown-retiring}'
Control descriptor is not initialized
perf: util/evsel.c:2028: get_group_fd: Assertion `!(!leader->core.fd)' failed.
Aborted
```
Thanks,
Ian
> Thanks,
> Tom
>
> > 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..1a5da93f4094 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_leader;
> > + cur_leaders_grp = &cur_leader->core;
> > if (pos_force_grouped)
> > force_grouped_leader = pos;
> > }
>
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