[PATCH V2 2/3] perf,tools: check and re-organize evsel cpu maps

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxx>

Some PMU events have cpumask, e.g uncore events. The cpu list set by
user may be incompatible with event's cpumask.
This patch will check the user defined cpu list. If the incompatible cpu
is found, it will warn the user and discard the incompatible cpu. Only
available cpu can be stored in evsel->cpus->map. If there is no cpu from
cpu list compatible with event's cpumask. It will error out.

Here is an example.
According to cpumask, uncore should be default on CPU0 and CPU18.
So the S0-C1 for uncore should show "<not counted>".

Without this patch
 $ sudo ./perf stat -e cycles,uncore_imc_0/cas_count_read/ -C0,1,18
--per-core sleep 2

 Performance counter stats for 'CPU(s) 0,1,18':

S0-C0           1            6749638      cycles
S0-C0           1               0.83 MiB  uncore_imc_0/cas_count_read/
(100.00%)
S0-C1           1             232421      cycles
S0-C1           1               0.83 MiB  uncore_imc_0/cas_count_read/
S1-C0           1             236997      cycles
S1-C0           1               0.35 MiB  uncore_imc_0/cas_count_read/

       2.001094019 seconds time elapsed

With this patch
 $ perf stat -e cycles,uncore_imc_0/cas_count_read/ -C0,1,18 --per-core
sleep 2
event uncore_imc_0/cas_count_read/ can only be monitored on CPU 0 18.
Other CPUs will be discard.

 Performance counter stats for 'CPU(s) 0,1,18':

S0-C0           1            5557406      cycles
S0-C0           1               0.21 MiB  uncore_imc_0/cas_count_read/
S0-C1           1            1012534      cycles
S0-C1           0      <not counted> MiB  uncore_imc_0/cas_count_read/
S1-C0           1             916130      cycles
S1-C0           1               0.08 MiB  uncore_imc_0/cas_count_read/

       2.001110843 seconds time elapsed

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---

Changes since V1
 - Re-implement the way to find the common cpus
 - Add test case

 tools/perf/util/evlist.c | 72 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 67 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 6cfdee6..d67414f 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1101,6 +1101,66 @@ int perf_evlist__mmap(struct perf_evlist *evlist, unsigned int pages,
 	return perf_evlist__mmap_ex(evlist, pages, overwrite, 0, false);
 }
 
+static int cmp_ids(const void *a, const void *b)
+{
+	return *(int *)a - *(int *)b;
+}
+
+static int perf_evlist__check_evsel_cpus(struct perf_evlist *evlist, struct perf_evsel *evsel)
+{
+	const int ncpus = cpu_map__nr(evlist->cpus);
+	int i = 0, j = 0, cpu_nr = 0, tmp;
+
+	/* ensure we process id in increasing order */
+	qsort(evlist->cpus->map, evlist->cpus->nr, sizeof(int), cmp_ids);
+
+	/* find the common cpus between evsel and evlist. */
+	while ((i < cpu_map__nr(evlist->cpus)) &&
+	       (j < cpu_map__nr(evsel->cpus))) {
+
+		if (evlist->cpus->map[i] == evsel->cpus->map[j]) {
+			cpu_nr++;
+			i++;
+			j++;
+		} else if (evlist->cpus->map[i] > evsel->cpus->map[j]) {
+			evsel->cpus->map[j++] = -1;
+		} else
+			i++;
+
+	}
+	while (j < cpu_map__nr(evsel->cpus))
+		evsel->cpus->map[j++] = -1;
+
+	if (cpu_nr == 0) {
+		pr_warning("event %s cannot be monitored on the given cpus."
+			   "Please check cpumask\n", evsel->name);
+		return -1;
+	}
+
+	if (ncpus > cpu_nr)
+		pr_warning("event %s can only be monitored on CPU", evsel->name);
+
+	/* order evsel cpus */
+	for (i = 0, tmp = 0; i < cpu_nr; i++) {
+		if (evsel->cpus->map[i] == -1) {
+			while (evsel->cpus->map[tmp] == -1) {
+				tmp++;
+				BUG_ON(tmp >= cpu_map__nr(evsel->cpus));
+			}
+			evsel->cpus->map[i] = evsel->cpus->map[tmp];
+			evsel->cpus->map[tmp] = -1;
+		}
+		if (ncpus > cpu_nr)
+			pr_warning(" %d", evsel->cpus->map[i]);
+		tmp++;
+	}
+	evsel->cpus->nr = cpu_nr;
+	if (ncpus > cpu_nr)
+		pr_warning(". Other CPUs will be discard.\n");
+
+	return 0;
+}
+
 static int perf_evlist__propagate_maps(struct perf_evlist *evlist,
 				       struct target *target)
 {
@@ -1108,13 +1168,15 @@ static int perf_evlist__propagate_maps(struct perf_evlist *evlist,
 
 	evlist__for_each(evlist, evsel) {
 		/*
-		 * We already have cpus for evsel (via PMU sysfs) so
-		 * keep it, if there's no target cpu list defined.
+		 * We already have cpus for evsel (via PMU sysfs)
+		 * and target cpu list defined, check if they are
+		 * compatible. If not, discard incompatible cpus.
 		 */
-		if (evsel->cpus && target->cpu_list)
-			cpu_map__put(evsel->cpus);
+		if (evsel->cpus && target->cpu_list &&
+		    perf_evlist__check_evsel_cpus(evlist, evsel))
+			return -EINVAL;
 
-		if (!evsel->cpus || target->cpu_list)
+		if (!evsel->cpus)
 			evsel->cpus = cpu_map__get(evlist->cpus);
 
 		evsel->threads = thread_map__get(evlist->threads);
-- 
1.8.3.1

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