[PATCH v1 02/14] libperf cpumap: Rename and prefer sysfs for perf_cpu_map__default_new
From: Ian Rogers
Date: Wed Nov 29 2023 - 01:02:28 EST
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>
---
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