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

Srikar Dronamraju
2022-04-08T12:27:04Z

* Athira Rajeev <atrajeev@linux.vnet.ibm.com> [2022-04-06 23:21:13]:

> 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>

Looks good to me.
Reviewed-by: Srikar Dronamraju <srikar@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
>