bpf: arraymap memory usage

Introduce array_map_mem_usage() to calculate arraymap memory usage. In
this helper, some small memory allocations are ignored, like the
allocation of struct bpf_array_aux in prog_array. The inner_map_meta in
array_of_map is also ignored.

The result as follows,

- before
11: array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524288B
12: percpu_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 8912896B
13: perf_event_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524288B
14: prog_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524288B
15: cgroup_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524288B

- after
11: array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524608B
12: percpu_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 17301824B
13: perf_event_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524608B
14: prog_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524608B
15: cgroup_array  name count_map  flags 0x0
        key 4B  value 4B  max_entries 65536  memlock 524608B
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230305124615.12358-5-laoar.shao@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/arraymap.c

@@ -721,6 +721,28 @@ static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_
 	return num_elems;
 }
 
+static u64 array_map_mem_usage(const struct bpf_map *map)
+{
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	bool percpu = map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY;
+	u32 elem_size = array->elem_size;
+	u64 entries = map->max_entries;
+	u64 usage = sizeof(*array);
+
+	if (percpu) {
+		usage += entries * sizeof(void *);
+		usage += entries * elem_size * num_possible_cpus();
+	} else {
+		if (map->map_flags & BPF_F_MMAPABLE) {
+			usage = PAGE_ALIGN(usage);
+			usage += PAGE_ALIGN(entries * elem_size);
+		} else {
+			usage += entries * elem_size;
+		}
+	}
+	return usage;
+}
+
 BTF_ID_LIST_SINGLE(array_map_btf_ids, struct, bpf_array)
 const struct bpf_map_ops array_map_ops = {
 	.map_meta_equal = array_map_meta_equal,
@@ -742,6 +764,7 @@ const struct bpf_map_ops array_map_ops = {
 	.map_update_batch = generic_map_update_batch,
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_array_elem,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
@@ -762,6 +785,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
 	.map_update_batch = generic_map_update_batch,
 	.map_set_for_each_callback_args = map_set_for_each_callback_args,
 	.map_for_each_callback = bpf_for_each_array_elem,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 	.iter_seq_info = &iter_seq_info,
 };
@@ -1156,6 +1180,7 @@ const struct bpf_map_ops prog_array_map_ops = {
 	.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
 	.map_release_uref = prog_array_map_clear,
 	.map_seq_show_elem = prog_array_map_seq_show_elem,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 };
 
@@ -1257,6 +1282,7 @@ const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_fd_put_ptr = perf_event_fd_array_put_ptr,
 	.map_release = perf_event_fd_array_release,
 	.map_check_btf = map_check_no_btf,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 };
 
@@ -1291,6 +1317,7 @@ const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_fd_get_ptr = cgroup_fd_array_get_ptr,
 	.map_fd_put_ptr = cgroup_fd_array_put_ptr,
 	.map_check_btf = map_check_no_btf,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 };
 #endif
@@ -1379,5 +1406,6 @@ const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_lookup_batch = generic_map_lookup_batch,
 	.map_update_batch = generic_map_update_batch,
 	.map_check_btf = map_check_no_btf,
+	.map_mem_usage = array_map_mem_usage,
 	.map_btf_id = &array_map_btf_ids[0],
 };