Linux网络性能优化与监控实战指南：从参数调优到请求分析

# 调整TCP监听队列长度（默认128，建议调大）
sysctl -w net.core.somaxconn=65535

# 保留特定端口（防止被随机占用）
sysctl -w net.ipv4.ip_local_reserved_ports=9100

# 调整本地端口范围（默认32768-60999）
sysctl -w net.ipv4.ip_local_port_range="1024 61999"

# 允许复用TIME-WAIT状态的端口
sysctl -w net.ipv4.tcp_tw_reuse=1

# 增加系统最大文件描述符数
sysctl -w fs.file-max=1048576

echo "net.core.somaxconn=65535" >> /etc/sysctl.conf
sysctl -p  # 重新加载配置

curl -w "
DNS解析  : %{time_namelookup}s
TCP连接 : %{time_connect}s
服务器处理: %{time_starttransfer}s
总耗时  : %{time_total}s\n" -o /dev/null -s http://example.com

DNS解析  : 0.012s
TCP连接 : 0.045s
服务器处理: 0.250s
总耗时  : 0.251s

ab -n 1000 -c 100 http://example.com/

watch -n 1 "ss -ant | awk 'NR>1 {print \$1}' | sort | uniq -c"

   ESTAB    500
   TIME-WAIT 200
   SYN-RECV  10

import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpRequestTimer {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpGet request = new HttpGet("http://example.com");

        long startTime = System.currentTimeMillis();
        try (CloseableHttpResponse response = httpClient.execute(request)) {
            long dnsTime = System.currentTimeMillis() - startTime;
            System.out.println("DNS + TCP Time: " + dnsTime + "ms");

            EntityUtils.consume(response.getEntity());
            long totalTime = System.currentTimeMillis() - startTime;
            System.out.println("Total Time: " + totalTime + "ms");
        }
    }
}

tcpdump -i eth0 -w http.pcap 'port 80'

# prometheus.yml
scrape_configs:
  - job_name: 'node'
    static_configs:
      - targets: ['localhost:9100']

ss -ant | grep -c 'TIME-WAIT'  # 返回数>10000

echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse
echo 30 > /proc/sys/net/ipv4/tcp_fin_timeout

ss -ant | grep -c 'SYN-RECV'  # 异常高

echo 2048 > /proc/sys/net/ipv4/tcp_max_syn_backlog
echo 1 > /proc/sys/net/ipv4/tcp_syncookies