Re: [PATCH V2 2/4] perf stat: Always keep perf metrics topdown events in a group
From: Liang, Kan
Date: Tue May 17 2022 - 09:44:04 EST
On 5/16/2022 11:11 PM, Ian Rogers wrote:
On Mon, May 16, 2022 at 8:25 AM <kan.liang@xxxxxxxxxxxxxxx> wrote:
From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
If any member in a group has a different cpu mask than the other
members, the current perf stat disables group. when the perf metrics
topdown events are part of the group, the below <not supported> error
will be triggered.
$ perf stat -e "{slots,topdown-retiring,uncore_imc_free_running_0/dclk/}" -a sleep 1
WARNING: grouped events cpus do not match, disabling group:
anon group { slots, topdown-retiring, uncore_imc_free_running_0/dclk/ }
Performance counter stats for 'system wide':
141,465,174 slots
<not supported> topdown-retiring
1,605,330,334 uncore_imc_free_running_0/dclk/
The perf metrics topdown events must always be grouped with a slots
event as leader.
Factor out evsel__remove_from_group() to only remove the regular events
from the group.
Remove evsel__must_be_in_group(), since no one use it anymore.
With the patch, the topdown events aren't broken from the group for the
splitting.
$ perf stat -e "{slots,topdown-retiring,uncore_imc_free_running_0/dclk/}" -a sleep 1
WARNING: grouped events cpus do not match, disabling group:
anon group { slots, topdown-retiring, uncore_imc_free_running_0/dclk/ }
Performance counter stats for 'system wide':
346,110,588 slots
124,608,256 topdown-retiring
1,606,869,976 uncore_imc_free_running_0/dclk/
1.003877592 seconds time elapsed
Fixes: a9a1790247bd ("perf stat: Ensure group is defined on top of the same cpu mask")
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
tools/perf/builtin-stat.c | 7 +++----
tools/perf/util/evlist.c | 6 +-----
tools/perf/util/evsel.c | 13 +++++++++++--
tools/perf/util/evsel.h | 2 +-
4 files changed, 16 insertions(+), 12 deletions(-)
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index a96f106dc93a..75c88c7939b1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -271,10 +271,9 @@ static void evlist__check_cpu_maps(struct evlist *evlist)
pr_warning(" %s: %s\n", evsel->name, buf);
}
- for_each_group_evsel(pos, leader) {
- evsel__set_leader(pos, pos);
- pos->core.nr_members = 0;
- }
+ for_each_group_evsel(pos, leader)
+ evsel__remove_from_group(pos, leader);
+
evsel->core.leader->nr_members = 0;
This shouldn't be necessary now.
It should point to itself which has been updated in
evsel__remove_from_group().
I will remove it in V3.
}
}
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index dfa65a383502..7fc544330fea 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1795,11 +1795,7 @@ struct evsel *evlist__reset_weak_group(struct evlist *evsel_list, struct evsel *
* them. Some events, like Intel topdown, require being
* in a group and so keep these in the group.
*/
- if (!evsel__must_be_in_group(c2) && c2 != leader) {
- evsel__set_leader(c2, c2);
- c2->core.nr_members = 0;
- leader->core.nr_members--;
- }
+ evsel__remove_from_group(c2, leader);
/*
* Set this for all former members of the group
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index b98882cbb286..deb428ee5e50 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -3083,7 +3083,16 @@ bool __weak arch_evsel__must_be_in_group(const struct evsel *evsel __maybe_unuse
return false;
}
-bool evsel__must_be_in_group(const struct evsel *evsel)
+/*
+ * Remove an event from a given group (leader).
+ * Some events, e.g., perf metrics Topdown events,
+ * must always be grouped. Ignore the events.
+ */
+void evsel__remove_from_group(struct evsel *evsel, struct evsel *leader)
{
- return arch_evsel__must_be_in_group(evsel);
+ if (!arch_evsel__must_be_in_group(evsel) && evsel != leader) {
+ evsel__set_leader(evsel, evsel);
+ evsel->core.nr_members = 0;
+ leader->core.nr_members--;
+ }
Should we also have:
if (leader->core.nr_members == 1)
leader->core.nr_members = 0;
Other wise say:
{instructions,cycles}
with a remove of cycles becomes:
{instructions}, cycles
rather than the previous:
instructions,cycles
Actually, looking at:
https://lore.kernel.org/lkml/20220512061308.1152233-2-irogers@xxxxxxxxxx/
+ /* Reset the leader count if all entries were removed. */
+ if (leader->core.nr_members)
+ leader->core.nr_members = 0;
is wrong and should be:
+ /* Reset the leader count if all entries were removed. */
+ if (leader->core.nr_members == 1)
+ leader->core.nr_members = 0;
For a perf metrics topdown group, the leader's nr_members must be > 1
after the reset. We should not clear it.
For the other weak group, the leader's nr_members should equal to 1
after the reset. We only need to clear it for this case.
I think it makes sense.
Thanks,
Kan
I'll fix and re-send.
> Thanks,
Ian
}
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index a36172ed4cf6..47f65f8e7c74 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -483,7 +483,7 @@ bool evsel__has_leader(struct evsel *evsel, struct evsel *leader);
bool evsel__is_leader(struct evsel *evsel);
void evsel__set_leader(struct evsel *evsel, struct evsel *leader);
int evsel__source_count(const struct evsel *evsel);
-bool evsel__must_be_in_group(const struct evsel *evsel);
+void evsel__remove_from_group(struct evsel *evsel, struct evsel *leader);
bool arch_evsel__must_be_in_group(const struct evsel *evsel);
--
2.35.1