libperf cpumap: Rename perf_cpu_map__default_new() to perf_cpu_map__new_online_cpus...

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 it 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.

Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andrew Jones <ajones@ventanamicro.com>
Cc: André Almeida <andrealmeid@igalia.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Atish Patra <atishp@rivosinc.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paran Lee <p4ranlee@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steinar H. Gunderson <sesse@google.com>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Cc: Yanteng Si <siyanteng@loongson.cn>
Cc: bpf@vger.kernel.org
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20231129060211.1890454-3-irogers@google.com
[ s/syfs/sysfs/g typo ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/perf/cpumap.c b/tools/lib/perf/cpumap.c
index 2bd6aba3d8c9af5e0d3043a604d81bbe07296ab9..3aa80d0d26e86949e9b37706654ff1f4c29bf3e5 100644 (file)
--- 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_sysfs_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_sysfs_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 d0bf218ada1190b2a8dcce1c7a2bf130761713b0..b24bd8b8f34e1c32758a6eb3765ab409949f842b 100644 (file)
--- 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 a8ff64baea3e1fd1450fac1394904997f4906c16..8a71f841498e4960a32347d02d750c8bde8291d6 100644 (file)
--- 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 2c359bdb951ee2bbc0d434ce88096993c7b3f704..c998b1dae86313d58134cf228552b66cf1a06e65 100644 (file)
--- 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;