High I/O wait on linux

[p5n]

Steps to reproduce: just start shadow-tls config -c /etc/shadow-tls/server.json and htop shows that 3 cpu cores are busy with I/O wait.

Config:

{
    "disable_nodelay": false,
    "fastopen": true,
    "v3": true,
    "strict": true,
    "server": {
        "listen": "0.0.0.0:5222",
        "server_addr": "127.0.0.1:5223",
        "tls_addr": {
            "wildcard_sni": "off",
            "dispatch": {
                "cloudflare.com": "1.1.1.1:443",
                "captive.apple.com": "captive.apple.com:443"
            },
            "fallback": "cloud.tencent.com:443"
        },
        "password": "*********",
        "wildcard_sni": "authed"
    }
}