[PATCH RFC 2/9] bpftool: show memcg info of bpf map

Yafang Shao
2022-03-08T13:11:18Z

bpf map can be charged to a memcg, so we'd better show the memcg info to
do better bpf memory management. This patch adds a new field
"memcg_state" to show whether a bpf map is charged to a memcg and
whether the memcg is offlined. Currently it has three values,
0 : not charged
-1 : the charged memcg is offline
1 : the charged memcg is online

For instance,

$ bpftool map show
2: array name iterator.rodata flags 0x480
key 4B value 98B max_entries 1 memlock 4096B
btf_id 240 frozen
memcg_state 0
3: hash name calico_failsafe flags 0x1
key 4B value 1B max_entries 65535 memlock 524288B
memcg_state 1
6: lru_hash name access_record flags 0x0
key 8B value 24B max_entries 102400 memlock 3276800B
btf_id 256
memcg_state -1

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/uapi/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 11 +++++++++++
tools/bpf/bpftool/map.c | 2 ++
tools/include/uapi/linux/bpf.h | 1 +
4 files changed, 15 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4eebea8..a448b06 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5864,6 +5864,7 @@ struct bpf_map_info {
__u32 btf_value_type_id;
__u32 :32; /* alignment pad */
__u64 map_extra;
+ __s8 memcg_state;
} __attribute__((aligned(8)));

struct bpf_btf_info {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index db402eb..3b50fcb 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3939,6 +3939,17 @@ static int bpf_map_get_info_by_fd(struct file *file,
}
info.btf_vmlinux_value_type_id = map->btf_vmlinux_value_type_id;

+#ifdef CONFIG_MEMCG_KMEM
+ if (map->memcg) {
+ struct mem_cgroup *memcg = map->memcg;
+
+ if (memcg == root_mem_cgroup)
+ info.memcg_state = 0;
+ else
+ info.memcg_state = memcg->kmemcg_id < 0 ? -1 : 1;
+ }
+#endif
+
if (bpf_map_is_dev_bound(map)) {
err = bpf_map_offload_info_fill(&info, map);
if (err)
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 0bba337..fe8322f 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -550,6 +550,7 @@ static int show_map_close_json(int fd, struct bpf_map_info *info)
jsonw_end_array(json_wtr);
}

+ jsonw_int_field(json_wtr, "memcg_state", info->memcg_state);
emit_obj_refs_json(refs_table, info->id, json_wtr);

jsonw_end_object(json_wtr);
@@ -635,6 +636,7 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
if (frozen)
printf("%sfrozen", info->btf_id ? " " : "");

+ printf("\n\tmemcg_state %d", info->memcg_state);
emit_obj_refs_plain(refs_table, info->id, "\n\tpids ");

printf("\n");
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4eebea8..41e65b3 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5864,6 +5864,7 @@ struct bpf_map_info {
__u32 btf_value_type_id;
__u32 :32; /* alignment pad */
__u64 map_extra;
+ __s8 memcg_state;
} __attribute__((aligned(8)));

struct bpf_btf_info {
--
1.8.3.1