On 29/11/2023 06:01, Ian Rogers wrote:
> Rename perf_cpu_map__default_new to perf_cpu_map__new_online_cpus to
> better indicate what the implementation does. Read the online CPUs
> from /sys/devices/system/cpu/online first before using sysconf as
> sysconf can't accurately configure holes in the CPU map. If sysconf is
> used, warn when the configured and online processors disagree.
>
> When reading from a file, if the read doesn't yield a CPU map then
> return an empty map rather than the default online. This avoids
> recursion but also better yields being able to detect failures.
>
> Add more comments.
>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
Reviewed-by: James Clark <james.clark@xxxxxxx>
> ---
> tools/lib/perf/cpumap.c | 59 +++++++++++++++++-----------
> tools/lib/perf/include/perf/cpumap.h | 15 ++++++-
> tools/lib/perf/libperf.map | 2 +-
> tools/lib/perf/tests/test-cpumap.c | 2 +-
> 4 files changed, 51 insertions(+), 27 deletions(-)
>
> diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
> index 2bd6aba3d8c9..463ca8b37d45 100644
> --- a/tools/lib/perf/cpumap.c
> +++ b/tools/lib/perf/cpumap.c
> @@ -9,6 +9,7 @@
> #include <unistd.h>
> #include <ctype.h>
> #include <limits.h>
> +#include "internal.h"
>
> void perf_cpu_map__set_nr(struct perf_cpu_map *map, int nr_cpus)
> {
> @@ -66,15 +67,21 @@ void perf_cpu_map__put(struct perf_cpu_map *map)
> }
> }
>
> -static struct perf_cpu_map *cpu_map__default_new(void)
> +static struct perf_cpu_map *cpu_map__new_sysconf(void)
> {
> struct perf_cpu_map *cpus;
> - int nr_cpus;
> + int nr_cpus, nr_cpus_conf;
>
> nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> if (nr_cpus < 0)
> return NULL;
>
> + nr_cpus_conf = sysconf(_SC_NPROCESSORS_CONF);
> + if (nr_cpus != nr_cpus_conf) {
> + pr_warning("Number of online CPUs (%d) differs from the number configured (%d) the CPU map will only cover the first %d CPUs.",
> + nr_cpus, nr_cpus_conf, nr_cpus);
> + }
> +
> cpus = perf_cpu_map__alloc(nr_cpus);
> if (cpus != NULL) {
> int i;
> @@ -86,9 +93,27 @@ static struct perf_cpu_map *cpu_map__default_new(void)
> return cpus;
> }
>
> -struct perf_cpu_map *perf_cpu_map__default_new(void)
> +static struct perf_cpu_map *cpu_map__new_syfs_online(void)
> {
> - return cpu_map__default_new();
> + struct perf_cpu_map *cpus = NULL;
> + FILE *onlnf;
> +
> + onlnf = fopen("/sys/devices/system/cpu/online", "r");
> + if (onlnf) {
> + cpus = perf_cpu_map__read(onlnf);
> + fclose(onlnf);
> + }
> + return cpus;
> +}
> +
> +struct perf_cpu_map *perf_cpu_map__new_online_cpus(void)
> +{
> + struct perf_cpu_map *cpus = cpu_map__new_syfs_online();
> +
> + if (cpus)
> + return cpus;
> +
> + return cpu_map__new_sysconf();
> }
>
>
> @@ -180,27 +205,11 @@ struct perf_cpu_map *perf_cpu_map__read(FILE *file)
>
> if (nr_cpus > 0)
> cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
> - else
> - cpus = cpu_map__default_new();
> out_free_tmp:
> free(tmp_cpus);
> return cpus;
> }
>
> -static struct perf_cpu_map *cpu_map__read_all_cpu_map(void)
> -{
> - struct perf_cpu_map *cpus = NULL;
> - FILE *onlnf;
> -
> - onlnf = fopen("/sys/devices/system/cpu/online", "r");
> - if (!onlnf)
> - return cpu_map__default_new();
> -
> - cpus = perf_cpu_map__read(onlnf);
> - fclose(onlnf);
> - return cpus;
> -}
> -
> struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
> {
> struct perf_cpu_map *cpus = NULL;
> @@ -211,7 +220,7 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
> int max_entries = 0;
>
> if (!cpu_list)
> - return cpu_map__read_all_cpu_map();
> + return perf_cpu_map__new_online_cpus();
>
> /*
> * must handle the case of empty cpumap to cover
> @@ -268,9 +277,11 @@ struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list)
>
> if (nr_cpus > 0)
> cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
> - else if (*cpu_list != '\0')
> - cpus = cpu_map__default_new();
> - else
> + else if (*cpu_list != '\0') {
> + pr_warning("Unexpected characters at end of cpu list ('%s'), using online CPUs.",
> + cpu_list);
> + cpus = perf_cpu_map__new_online_cpus();
> + } else
> cpus = perf_cpu_map__new_any_cpu();
> invalid:
> free(tmp_cpus);
> diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
> index d0bf218ada11..b24bd8b8f34e 100644
> --- a/tools/lib/perf/include/perf/cpumap.h
> +++ b/tools/lib/perf/include/perf/cpumap.h
> @@ -22,7 +22,20 @@ struct perf_cpu_map;
> * perf_cpu_map__new_any_cpu - a map with a singular "any CPU"/dummy -1 value.
> */
> LIBPERF_API struct perf_cpu_map *perf_cpu_map__new_any_cpu(void);
> -LIBPERF_API struct perf_cpu_map *perf_cpu_map__default_new(void);
> +/**
> + * perf_cpu_map__new_online_cpus - a map read from
> + * /sys/devices/system/cpu/online if
> + * available. If reading wasn't possible a map
> + * is created using the online processors
> + * assuming the first 'n' processors are all
> + * online.
> + */
> +LIBPERF_API struct perf_cpu_map *perf_cpu_map__new_online_cpus(void);
> +/**
> + * perf_cpu_map__new - create a map from the given cpu_list such as "0-7". If no
> + * cpu_list argument is provided then
> + * perf_cpu_map__new_online_cpus is returned.
> + */
> LIBPERF_API struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list);
> LIBPERF_API struct perf_cpu_map *perf_cpu_map__read(FILE *file);
> LIBPERF_API struct perf_cpu_map *perf_cpu_map__get(struct perf_cpu_map *map);
> diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> index a8ff64baea3e..8a71f841498e 100644
> --- a/tools/lib/perf/libperf.map
> +++ b/tools/lib/perf/libperf.map
> @@ -2,7 +2,7 @@ LIBPERF_0.0.1 {
> global:
> libperf_init;
> perf_cpu_map__new_any_cpu;
> - perf_cpu_map__default_new;
> + perf_cpu_map__new_online_cpus;
> perf_cpu_map__get;
> perf_cpu_map__put;
> perf_cpu_map__new;
> diff --git a/tools/lib/perf/tests/test-cpumap.c b/tools/lib/perf/tests/test-cpumap.c
> index 2c359bdb951e..c998b1dae863 100644
> --- a/tools/lib/perf/tests/test-cpumap.c
> +++ b/tools/lib/perf/tests/test-cpumap.c
> @@ -29,7 +29,7 @@ int test_cpumap(int argc, char **argv)
> perf_cpu_map__put(cpus);
> perf_cpu_map__put(cpus);
>
> - cpus = perf_cpu_map__default_new();
> + cpus = perf_cpu_map__new_online_cpus();
> if (!cpus)
> return -1;
>
