perf stat: Print out hint for mixed PMU group error

Perf doesn't support mixed events from different PMUs (except software
event) in a group. For this case, only "<not counted>" or "<not
supported>" are printed out. There is no hint which guides users to fix
the issue.

Checking the PMU type of events to determine if they are from the same
PMU. There may be false alarm for the checking. E.g. the core PMU has
different PMU type. But it should not happen often.

The false alarm can also be tolerated, because:

- It only happens on error path.
- It just provides a possible solution for the issue.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Agustin Vega-Frias <agustinv@codeaurora.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1524594014-79243-2-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 147a27e8c937cdb5b81c6929f2896e97623cee28..30e6b374e0953fceaf7b7ef7b9191ccf46e6a048 100644 (file)
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -172,6 +172,7 @@ static bool                 interval_count;
 static const char              *output_name;
 static int                     output_fd;
 static int                     print_free_counters_hint;
+static int                     print_mixed_hw_group_error;
 
 struct perf_stat {
        bool                     record;
@@ -1126,6 +1127,30 @@ static void abs_printout(int id, int nr, struct perf_evsel *evsel, double avg)
                fprintf(output, "%s%s", csv_sep, evsel->cgrp->name);
 }
 
+static bool is_mixed_hw_group(struct perf_evsel *counter)
+{
+       struct perf_evlist *evlist = counter->evlist;
+       u32 pmu_type = counter->attr.type;
+       struct perf_evsel *pos;
+
+       if (counter->nr_members < 2)
+               return false;
+
+       evlist__for_each_entry(evlist, pos) {
+               /* software events can be part of any hardware group */
+               if (pos->attr.type == PERF_TYPE_SOFTWARE)
+                       continue;
+               if (pmu_type == PERF_TYPE_SOFTWARE) {
+                       pmu_type = pos->attr.type;
+                       continue;
+               }
+               if (pmu_type != pos->attr.type)
+                       return true;
+       }
+
+       return false;
+}
+
 static void printout(int id, int nr, struct perf_evsel *counter, double uval,
                     char *prefix, u64 run, u64 ena, double noise,
                     struct runtime_stat *st)
@@ -1178,8 +1203,11 @@ static void printout(int id, int nr, struct perf_evsel *counter, double uval,
                        counter->supported ? CNTR_NOT_COUNTED : CNTR_NOT_SUPPORTED,
                        csv_sep);
 
-               if (counter->supported)
+               if (counter->supported) {
                        print_free_counters_hint = 1;
+                       if (is_mixed_hw_group(counter))
+                               print_mixed_hw_group_error = 1;
+               }
 
                fprintf(stat_config.output, "%-*s%s",
                        csv_output ? 0 : unit_width,
@@ -1757,6 +1785,11 @@ static void print_footer(void)
 "      echo 0 > /proc/sys/kernel/nmi_watchdog\n"
 "      perf stat ...\n"
 "      echo 1 > /proc/sys/kernel/nmi_watchdog\n");
+
+       if (print_mixed_hw_group_error)
+               fprintf(output,
+                       "The events in group usually have to be from "
+                       "the same PMU. Try reorganizing the group.\n");
 }
 
 static void print_counters(struct timespec *ts, int argc, const char **argv)