每个CPU阵列的BPF是否未初始化为零?

我想用a BPF_MAP_TYPE_PERCPU_ARRAY 统计在 SK_SKB 钩子。我用以下方式检查了地图值 bpftool map dump 在创建映射后,似乎对于某些CPU,值没有初始化为零。

以下是地图定义:

struct {
  __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
  __uint(max_entries, 1);
  __type(key, int);
  __type(value, __u64);
  __uint(pinning, LIBBPF_PIN_BY_NAME);
} request_count_map SEC(".maps");

以下是输出 bpftool地图转储 :

$ sudo bpftool map dump id 287
[{
        "key": 0,
        "values": [{
                "cpu": 0,
                "value": 0
            },{
                "cpu": 1,
                "value": 94322157119214
            },{
                "cpu": 2,
                "value": 140730068914171
            },{
                "cpu": 3,
                "value": 94322160575280
            },{
                "cpu": 4,
                "value": 94322160592312
            },{
                "cpu": 5,
                "value": 94322160592512
            },{
                "cpu": 6,
                "value": 80
            },{
                "cpu": 7,
                "value": 0
            },{
                "cpu": 8,
                "value": 0
            },{
                "cpu": 9,
                "value": 140730068932048
            },{
                "cpu": 10,
                "value": 0
            },{
                "cpu": 11,
                "value": 0
            },{
                "cpu": 12,
                "value": 0
            },{
                "cpu": 13,
                "value": 0
            },{
                "cpu": 14,
                "value": 0
            },{
                "cpu": 15,
                "value": 0
            },{
                "cpu": 16,
                "value": 80
            },{
                "cpu": 17,
                "value": 0
            },{
                "cpu": 18,
                "value": 0
            },{
                "cpu": 19,
                "value": 140730068932048
            }
        ]
    }
]

从文档中( here 和 here ),似乎预期的行为是将值初始化为零?

编辑: 加载地图时,我意识到我正在更新地图,如下所示:

int index = 0;
__u64 value = 0;

// Get the svc_identifier_map fd.
reqcnt_map_fd = bpf_obj_get(reqcnt_map_filename);

// Add the svc identifier to the svc_identifier_map.
err = bpf_map_update_elem(respcnt_map_fd, &index, &value, BPF_ANY);
if (err) {
  goto fail;
}

然而,这些值仍然应该是零吗?