[PATCH v2 4/4] tools/perf: Fix perf bench numa testcase to check if CPU used to bind task is online

Athira Rajeev
2022-04-06T20:02:18Z

Perf numa bench test fails with error:

Testcase:
./perf bench numa mem -p 2 -t 1 -P 1024 -C 0,8 -M 1,0 -s 20 -zZq
--thp 1 --no-data_rand_walk

Failure snippet:
<<>>
Running 'numa/mem' benchmark:

# Running main, "perf bench numa numa-mem -p 2 -t 1 -P 1024 -C 0,8
-M 1,0 -s 20 -zZq --thp 1 --no-data_rand_walk"

perf: bench/numa.c:333: bind_to_cpumask: Assertion `!(ret)' failed.
<<>>

The Testcases uses CPU’s 0 and 8. In function "parse_setup_cpu_list",
There is check to see if cpu number is greater than max cpu’s possible
in the system ie via "if (bind_cpu_0 >= g->p.nr_cpus ||
bind_cpu_1 >= g->p.nr_cpus) {". But it could happen that system has
say 48 CPU’s, but only number of online CPU’s is 0-7. Other CPU’s
are offlined. Since "g->p.nr_cpus" is 48, so function will go ahead
and set bit for CPU 8 also in cpumask ( td->bind_cpumask).

bind_to_cpumask function is called to set affinity using
sched_setaffinity and the cpumask. Since the CPU8 is not present,
set affinity will fail here with EINVAL. Fix this issue by adding a
check to make sure that, CPU’s provided in the input argument values
are online before proceeding further and skip the test. For this,
include new helper function "is_cpu_online" in
"tools/perf/util/header.c".

Since "BIT(x)" definition will get included from header.h, remove
that from bench/numa.c

Tested-by: Disha Goel <disgoel@linux.vnet.ibm.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reported-by: Disha Goel <disgoel@linux.vnet.ibm.com>
---
tools/perf/bench/numa.c | 8 ++++++--
tools/perf/util/header.c | 43 ++++++++++++++++++++++++++++++++++++++++
tools/perf/util/header.h | 1 +
3 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index 29e41e32bd88..7992d79b3e41 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -34,6 +34,7 @@
#include <linux/numa.h>
#include <linux/zalloc.h>

+#include "../util/header.h"
#include <numa.h>
#include <numaif.h>

@@ -616,6 +617,11 @@ static int parse_setup_cpu_list(void)
return -1;
}

+ if (is_cpu_online(bind_cpu_0) != 1 || is_cpu_online(bind_cpu_1) != 1) {
+ printf("\nTest not applicable, bind_cpu_0 or bind_cpu_1 is offline\n");
+ return -1;
+ }
+
BUG_ON(bind_cpu_0 < 0 || bind_cpu_1 < 0);
BUG_ON(bind_cpu_0 > bind_cpu_1);

@@ -786,8 +792,6 @@ static int parse_nodes_opt(const struct option *opt __maybe_unused,
return parse_node_list(arg);
}

-#define BIT(x) (1ul << x)
-
static inline uint32_t lfsr_32(uint32_t lfsr)
{
const uint32_t taps = BIT(1) | BIT(5) | BIT(6) | BIT(31);
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 6da12e522edc..3f5fcf5d4b3f 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -983,6 +983,49 @@ static int write_dir_format(struct feat_fd *ff,
return do_write(ff, &data->dir.version, sizeof(data->dir.version));
}

+#define SYSFS "/sys/devices/system/cpu/"
+
+/*
+ * Check whether a CPU is online
+ *
+ * Returns:
+ * 1 -> if CPU is online
+ * 0 -> if CPU is offline
+ * -1 -> error case
+ */
+int is_cpu_online(unsigned int cpu)
+{
+ char sysfs_cpu[255];
+ char buf[255];
+ struct stat statbuf;
+ size_t len;
+ int fd;
+
+ snprintf(sysfs_cpu, sizeof(sysfs_cpu), SYSFS "cpu%u", cpu);
+
+ if (stat(sysfs_cpu, &statbuf) != 0)
+ return 0;
+
+ /*
+ * Check if /sys/devices/system/cpu/cpux/online file
+ * exists. In kernels without CONFIG_HOTPLUG_CPU, this
+ * file won't exist.
+ */
+ snprintf(sysfs_cpu, sizeof(sysfs_cpu), SYSFS "cpu%u/online", cpu);
+ if (stat(sysfs_cpu, &statbuf) != 0)
+ return 1;
+
+ fd = open(sysfs_cpu, O_RDONLY);
+ if (fd == -1)
+ return -1;
+
+ len = read(fd, buf, sizeof(buf) - 1);
+ buf[len] = '\0';
+ close(fd);
+
+ return strtoul(buf, NULL, 16);
+}
+
#ifdef HAVE_LIBBPF_SUPPORT
static int write_bpf_prog_info(struct feat_fd *ff,
struct evlist *evlist __maybe_unused)
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index c9e3265832d9..0eb4bc29a5a4 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -158,6 +158,7 @@ int do_write(struct feat_fd *fd, const void *buf, size_t size);
int write_padded(struct feat_fd *fd, const void *bf,
size_t count, size_t count_aligned);

+int is_cpu_online(unsigned int cpu);
/*
* arch specific callback
*/
--
2.35.1