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    Subject[PATCH v1 02/14] libperf cpumap: Rename and prefer sysfs for perf_cpu_map__default_new
    From
    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@google.com>
    ---
    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;

    --
    2.43.0.rc1.413.gea7ed67945-goog
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