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* [PATCH] tools/perf/tests: Update perf record testcase to fix usage of affinity for machines with #CPUs > 1K
@ 2025-08-14 11:49 Athira Rajeev
  2025-08-14 12:23 ` Venkat
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Athira Rajeev @ 2025-08-14 11:49 UTC (permalink / raw)
  To: acme, jolsa, adrian.hunter, irogers, namhyung
  Cc: linux-perf-users, maddy, atrajeev, kjain, hbathini,
	Aditya.Bodkhe1, Tejas Manhas

The perf record testcase fails on systems with more than 1K CPUs.

Testcase: perf test -vv "PERF_RECORD_* events & perf_sample fields"

  PERF_RECORD_* events & perf_sample fields                       :
  --- start ---
  test child forked, pid 272482
  sched_getaffinity: Invalid argument
  sched__get_first_possible_cpu: Invalid argument
  test child finished with -1
  ---- end ----
  PERF_RECORD_* events & perf_sample fields: FAILED!

sched__get_first_possible_cpu uses "sched_getaffinity" to get the
cpumask and this call is returning EINVAL (Invalid argument).
This happens because the default mask size in glibc is 1024.  To
overcome this 1024 CPUs mask size limitation of cpu_set_t, change the
mask size using the CPU_*_S macros ie, use CPU_ALLOC to allocate
cpumask, CPU_ALLOC_SIZE for size. Same fix needed for mask which is
used to setaffinity so that mask size is large enough to represent
number of possible CPU's in the system.

Reported-by: Tejas Manhas <tejas05@linux.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
---
 tools/perf/tests/perf-record.c | 36 ++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/tools/perf/tests/perf-record.c b/tools/perf/tests/perf-record.c
index 0b3c37e66871..d895df037707 100644
--- a/tools/perf/tests/perf-record.c
+++ b/tools/perf/tests/perf-record.c
@@ -13,15 +13,19 @@
 #include "tests.h"
 #include "util/mmap.h"
 #include "util/sample.h"
+#include "util/cpumap.h"
 
 static int sched__get_first_possible_cpu(pid_t pid, cpu_set_t *maskp)
 {
-	int i, cpu = -1, nrcpus = 1024;
+	int i, cpu = -1;
+	int nrcpus = cpu__max_cpu().cpu;
+	size_t size = CPU_ALLOC_SIZE(nrcpus);
+
 realloc:
-	CPU_ZERO(maskp);
+	CPU_ZERO_S(size, maskp);
 
-	if (sched_getaffinity(pid, sizeof(*maskp), maskp) == -1) {
-		if (errno == EINVAL && nrcpus < (1024 << 8)) {
+	if (sched_getaffinity(pid, size, maskp) == -1) {
+		if (errno == EINVAL && nrcpus < (cpu__max_cpu().cpu << 8)) {
 			nrcpus = nrcpus << 2;
 			goto realloc;
 		}
@@ -30,11 +34,11 @@ static int sched__get_first_possible_cpu(pid_t pid, cpu_set_t *maskp)
 	}
 
 	for (i = 0; i < nrcpus; i++) {
-		if (CPU_ISSET(i, maskp)) {
+		if (CPU_ISSET_S(i, size, maskp)) {
 			if (cpu == -1)
 				cpu = i;
 			else
-				CPU_CLR(i, maskp);
+				CPU_CLR_S(i, size, maskp);
 		}
 	}
 
@@ -50,8 +54,9 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 		.no_buffering = true,
 		.mmap_pages   = 256,
 	};
-	cpu_set_t cpu_mask;
-	size_t cpu_mask_size = sizeof(cpu_mask);
+	int nrcpus = cpu__max_cpu().cpu;
+	cpu_set_t *cpu_mask;
+	size_t cpu_mask_size;
 	struct evlist *evlist = evlist__new_dummy();
 	struct evsel *evsel;
 	struct perf_sample sample;
@@ -69,12 +74,22 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 	int total_events = 0, nr_events[PERF_RECORD_MAX] = { 0, };
 	char sbuf[STRERR_BUFSIZE];
 
+	cpu_mask = CPU_ALLOC(nrcpus);
+	if (!cpu_mask) {
+		pr_debug("failed to create cpumask\n");
+		goto out;
+	}
+
+	cpu_mask_size = CPU_ALLOC_SIZE(nrcpus);
+	CPU_ZERO_S(cpu_mask_size, cpu_mask);
+
 	perf_sample__init(&sample, /*all=*/false);
 	if (evlist == NULL) /* Fallback for kernels lacking PERF_COUNT_SW_DUMMY */
 		evlist = evlist__new_default();
 
 	if (evlist == NULL) {
 		pr_debug("Not enough memory to create evlist\n");
+		CPU_FREE(cpu_mask);
 		goto out;
 	}
 
@@ -111,7 +126,7 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 	evsel__set_sample_bit(evsel, TIME);
 	evlist__config(evlist, &opts, NULL);
 
-	err = sched__get_first_possible_cpu(evlist->workload.pid, &cpu_mask);
+	err = sched__get_first_possible_cpu(evlist->workload.pid, cpu_mask);
 	if (err < 0) {
 		pr_debug("sched__get_first_possible_cpu: %s\n",
 			 str_error_r(errno, sbuf, sizeof(sbuf)));
@@ -123,7 +138,7 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 	/*
 	 * So that we can check perf_sample.cpu on all the samples.
 	 */
-	if (sched_setaffinity(evlist->workload.pid, cpu_mask_size, &cpu_mask) < 0) {
+	if (sched_setaffinity(evlist->workload.pid, cpu_mask_size, cpu_mask) < 0) {
 		pr_debug("sched_setaffinity: %s\n",
 			 str_error_r(errno, sbuf, sizeof(sbuf)));
 		goto out_delete_evlist;
@@ -328,6 +343,7 @@ static int test__PERF_RECORD(struct test_suite *test __maybe_unused, int subtest
 		++errs;
 	}
 out_delete_evlist:
+	CPU_FREE(cpu_mask);
 	evlist__delete(evlist);
 out:
 	perf_sample__exit(&sample);
-- 
2.43.7


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-08-20 17:23 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2025-08-14 11:49 [PATCH] tools/perf/tests: Update perf record testcase to fix usage of affinity for machines with #CPUs > 1K Athira Rajeev
2025-08-14 12:23 ` Venkat
2025-08-14 20:23 ` Namhyung Kim
2025-08-20 17:20   ` Athira Rajeev
2025-08-19 11:56 ` tejas05
2025-08-20 17:22   ` Athira Rajeev

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