| Message ID | 20190626061235.602633-3-andriin@fb.com |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | libbpf: add perf buffer abstraction and API | expand |
> On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andriin@fb.com> wrote: > > For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of > possible CPUs. This is impossible to specify at compilation time. This > change adds automatic setting of PERF_EVENT_ARRAY size to number of > system CPUs, unless non-zero size is specified explicitly. This allows > to adjust size for advanced specific cases, while providing convenient > and logical defaults. > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > --- > tools/lib/bpf/libbpf.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index c74cc535902a..8f2b8a081ba7 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -2114,6 +2114,7 @@ static int > bpf_object__create_maps(struct bpf_object *obj) > { > struct bpf_create_map_attr create_attr = {}; > + int nr_cpus = 0; > unsigned int i; > int err; > > @@ -2136,7 +2137,21 @@ bpf_object__create_maps(struct bpf_object *obj) > create_attr.map_flags = def->map_flags; > create_attr.key_size = def->key_size; > create_attr.value_size = def->value_size; > - create_attr.max_entries = def->max_entries; > + if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && > + !def->max_entries) { > + if (!nr_cpus) > + nr_cpus = libbpf_num_possible_cpus(); > + if (nr_cpus < 0) { > + pr_warning("failed to determine number of system CPUs: %d\n", > + nr_cpus); > + return nr_cpus; I think we need to goto err_out here. Thanks, Song
On Wed, Jun 26, 2019 at 11:57 AM Song Liu <songliubraving@fb.com> wrote: > > > > > On Jun 25, 2019, at 11:12 PM, Andrii Nakryiko <andriin@fb.com> wrote: > > > > For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of > > possible CPUs. This is impossible to specify at compilation time. This > > change adds automatic setting of PERF_EVENT_ARRAY size to number of > > system CPUs, unless non-zero size is specified explicitly. This allows > > to adjust size for advanced specific cases, while providing convenient > > and logical defaults. > > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > --- > > tools/lib/bpf/libbpf.c | 17 ++++++++++++++++- > > 1 file changed, 16 insertions(+), 1 deletion(-) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index c74cc535902a..8f2b8a081ba7 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -2114,6 +2114,7 @@ static int > > bpf_object__create_maps(struct bpf_object *obj) > > { > > struct bpf_create_map_attr create_attr = {}; > > + int nr_cpus = 0; > > unsigned int i; > > int err; > > > > @@ -2136,7 +2137,21 @@ bpf_object__create_maps(struct bpf_object *obj) > > create_attr.map_flags = def->map_flags; > > create_attr.key_size = def->key_size; > > create_attr.value_size = def->value_size; > > - create_attr.max_entries = def->max_entries; > > + if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && > > + !def->max_entries) { > > + if (!nr_cpus) > > + nr_cpus = libbpf_num_possible_cpus(); > > + if (nr_cpus < 0) { > > + pr_warning("failed to determine number of system CPUs: %d\n", > > + nr_cpus); > > + return nr_cpus; > > I think we need to goto err_out here. Absolutely, good catch, thanks! > > Thanks, > Song >
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index c74cc535902a..8f2b8a081ba7 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -2114,6 +2114,7 @@ static int bpf_object__create_maps(struct bpf_object *obj) { struct bpf_create_map_attr create_attr = {}; + int nr_cpus = 0; unsigned int i; int err; @@ -2136,7 +2137,21 @@ bpf_object__create_maps(struct bpf_object *obj) create_attr.map_flags = def->map_flags; create_attr.key_size = def->key_size; create_attr.value_size = def->value_size; - create_attr.max_entries = def->max_entries; + if (def->type == BPF_MAP_TYPE_PERF_EVENT_ARRAY && + !def->max_entries) { + if (!nr_cpus) + nr_cpus = libbpf_num_possible_cpus(); + if (nr_cpus < 0) { + pr_warning("failed to determine number of system CPUs: %d\n", + nr_cpus); + return nr_cpus; + } + pr_debug("map '%s': setting size to %d\n", + map->name, nr_cpus); + create_attr.max_entries = nr_cpus; + } else { + create_attr.max_entries = def->max_entries; + } create_attr.btf_fd = 0; create_attr.btf_key_type_id = 0; create_attr.btf_value_type_id = 0;
For BPF_MAP_TYPE_PERF_EVENT_ARRAY typically correct size is number of possible CPUs. This is impossible to specify at compilation time. This change adds automatic setting of PERF_EVENT_ARRAY size to number of system CPUs, unless non-zero size is specified explicitly. This allows to adjust size for advanced specific cases, while providing convenient and logical defaults. Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/lib/bpf/libbpf.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)