perf bench: Fix numa testcase to check if CPU used to bind task is online

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

Reported-by: Disha Goel <disgoel@linux.vnet.ibm.com>
Signed-off-by: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nageswara R Sastry <rnsastry@linux.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20220412164059.42654-2-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index f2640179ada9edb617bbbd7ad4fab7691f224004..c838c248aa2cd0ddbcb163a07d51998fb1c54fb6 100644 (file)
--- 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>
 
@@ -585,6 +586,11 @@ 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);
 
@@ -752,8 +758,6 @@ 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 d546ff724dbe250c78784758959c3bfe630597ee..a27132e5a5efee55a2936ecb14b0044a13d57c7b 100644 (file)
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -983,6 +983,57 @@ static int write_dir_format(struct feat_fd *ff,
        return do_write(ff, &data->dir.version, sizeof(data->dir.version));
 }
 
+/*
+ * 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 *str;
+       size_t strlen;
+       char buf[256];
+       int status = -1;
+       struct stat statbuf;
+
+       snprintf(buf, sizeof(buf),
+               "/sys/devices/system/cpu/cpu%d", cpu);
+       if (stat(buf, &statbuf) != 0)
+               return 0;
+
+       /*
+        * Check if /sys/devices/system/cpu/cpux/online file
+        * exists. Some cases cpu0 won't have online file since
+        * it is not expected to be turned off generally.
+        * In kernels without CONFIG_HOTPLUG_CPU, this
+        * file won't exist
+        */
+       snprintf(buf, sizeof(buf),
+               "/sys/devices/system/cpu/cpu%d/online", cpu);
+       if (stat(buf, &statbuf) != 0)
+               return 1;
+
+       /*
+        * Read online file using sysfs__read_str.
+        * If read or open fails, return -1.
+        * If read succeeds, return value from file
+        * which gets stored in "str"
+        */
+       snprintf(buf, sizeof(buf),
+               "devices/system/cpu/cpu%d/online", cpu);
+
+       if (sysfs__read_str(buf, &str, &strlen) < 0)
+               return status;
+
+       status = atoi(str);
+
+       free(str);
+       return status;
+}
+
 #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 c9e3265832d92c1d44a1833e4e2880d4a1bf8c60..0eb4bc29a5a46c2862f49ec4058712a644f3565b 100644 (file)
--- 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
  */