perf evlist: Keep topdown counters in weak group

On Intel Icelake, topdown events must always be grouped with a slots
event as leader. When a metric is parsed a weak group is formed and
retried if perf_event_open fails. The retried events aren't grouped
breaking the slots leader requirement. This change modifies the weak
group "reset" behavior so that topdown events aren't broken from the
group for the retry.

  $ perf stat -e '{slots,topdown-bad-spec,topdown-be-bound,topdown-fe-bound,topdown-retiring,branch-instructions,branch-misses,bus-cycles,cache-misses,cache-references,cpu-cycles,instructions,mem-loads,mem-stores,ref-cycles,baclears.any,ARITH.DIVIDER_ACTIVE}:W' -a sleep 1

   Performance counter stats for 'system wide':

    47,867,188,483      slots                                                         (92.27%)
   <not supported>      topdown-bad-spec
   <not supported>      topdown-be-bound
   <not supported>      topdown-fe-bound
   <not supported>      topdown-retiring
     2,173,346,937      branch-instructions                                           (92.27%)
        10,540,253      branch-misses             #    0.48% of all branches          (92.29%)
        96,291,140      bus-cycles                                                    (92.29%)
         6,214,202      cache-misses              #   20.120 % of all cache refs      (92.29%)
        30,886,082      cache-references                                              (76.91%)
    11,773,726,641      cpu-cycles                                                    (84.62%)
    11,807,585,307      instructions              #    1.00  insn per cycle           (92.31%)
                 0      mem-loads                                                     (92.32%)
     2,212,928,573      mem-stores                                                    (84.69%)
    10,024,403,118      ref-cycles                                                    (92.35%)
        16,232,978      baclears.any                                                  (92.35%)
        23,832,633      ARITH.DIVIDER_ACTIVE                                          (84.59%)

       0.981070734 seconds time elapsed

After:

  $ perf stat -e '{slots,topdown-bad-spec,topdown-be-bound,topdown-fe-bound,topdown-retiring,branch-instructions,branch-misses,bus-cycles,cache-misses,cache-references,cpu-cycles,instructions,mem-loads,mem-stores,ref-cycles,baclears.any,ARITH.DIVIDER_ACTIVE}:W' -a sleep 1

   Performance counter stats for 'system wide':

       31040189283      slots                                                         (92.27%)
        8997514811      topdown-bad-spec          #     28.2% bad speculation         (92.27%)
       10997536028      topdown-be-bound          #     34.5% backend bound           (92.27%)
        4778060526      topdown-fe-bound          #     15.0% frontend bound          (92.27%)
        7086628768      topdown-retiring          #     22.2% retiring                (92.27%)
        1417611942      branch-instructions                                           (92.26%)
           5285529      branch-misses             #    0.37% of all branches          (92.28%)
          62922469      bus-cycles                                                    (92.29%)
           1440708      cache-misses              #    8.292 % of all cache refs      (92.30%)
          17374098      cache-references                                              (76.94%)
        8040889520      cpu-cycles                                                    (84.63%)
        7709992319      instructions              #    0.96  insn per cycle           (92.32%)
                 0      mem-loads                                                     (92.32%)
        1515669558      mem-stores                                                    (84.68%)
        6542411177      ref-cycles                                                    (92.35%)
           4154149      baclears.any                                                  (92.35%)
          20556152      ARITH.DIVIDER_ACTIVE                                          (84.59%)

       1.010799593 seconds time elapsed
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Florian Fischer <florian.fischer@muhq.space>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220517052724.283874-2-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/x86/util/evsel.c

@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include "util/evsel.h"
 #include "util/env.h"
+#include "util/pmu.h"
 #include "linux/string.h"
 
 void arch_evsel__set_sample_weight(struct evsel *evsel)
@@ -29,3 +30,14 @@ void arch_evsel__fixup_new_cycles(struct perf_event_attr *attr)
 
 	free(env.cpuid);
 }
+
+bool arch_evsel__must_be_in_group(const struct evsel *evsel)
+{
+	if ((evsel->pmu_name && strcmp(evsel->pmu_name, "cpu")) ||
+	    !pmu_have_event("cpu", "slots"))
+		return false;
+
+	return evsel->name &&
+		(!strcasecmp(evsel->name, "slots") ||
+		 strcasestr(evsel->name, "topdown"));
+}

tools/perf/util/evlist.c

@@ -1742,8 +1742,17 @@ struct evsel *evlist__reset_weak_group(struct evlist *evsel_list, struct evsel *
 		if (evsel__has_leader(c2, leader)) {
 			if (is_open && close)
 				perf_evsel__close(&c2->core);
-			evsel__set_leader(c2, c2);
-			c2->core.nr_members = 0;
+			/*
+			 * We want to close all members of the group and reopen
+			 * 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--;
+			}
+
 			/*
 			 * Set this for all former members of the group
 			 * to indicate they get reopened.
@@ -1751,6 +1760,9 @@ struct evsel *evlist__reset_weak_group(struct evlist *evsel_list, struct evsel *
 			c2->reset_group = true;
 		}
 	}
+	/* Reset the leader count if all entries were removed. */
+	if (leader->core.nr_members == 1)
+		leader->core.nr_members = 0;
 	return leader;
 }
 

tools/perf/util/evsel.c

@@ -3103,3 +3103,13 @@ int evsel__source_count(const struct evsel *evsel)
 	}
 	return count;
 }
+
+bool __weak arch_evsel__must_be_in_group(const struct evsel *evsel __maybe_unused)
+{
+	return false;
+}
+
+bool evsel__must_be_in_group(const struct evsel *evsel)
+{
+	return arch_evsel__must_be_in_group(evsel);
+}

tools/perf/util/evsel.h

@@ -499,6 +499,9 @@ 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);
+
+bool arch_evsel__must_be_in_group(const struct evsel *evsel);
 
 /*
  * Macro to swap the bit-field postition and size.