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linux - 大的发送套接字缓冲区大小导致 UDP 数据包丢失

问题描述

操作系统：Centos7.6.10 内核：3.10.0-957.el7.x86_64 我用netperf测试UDP。当我设置发送套接字大小8129920;接收套接字大小212992时，UDP数据包丢失很多。只有大数据包才会在这个问题上。两台电脑的netperf测试，然后我尝试tcpdump，我发现发送的UDP数据不完整，总是缺少一个IP帧，以至于对方无法合并这些帧。tcpdump 结果我在发送方 PC 上使用 dropwatch 来查找内核问题，我找到了这些

1581 drops at brk_limit+369bd232 (0xffffffffc0437232)
1 drops at skb_queue_purge+18 (0xffffffff88a235d8)
1632 drops at brk_limit+369bd232 (0xffffffffc0437232)
1682 drops at brk_limit+369bd232 (0xffffffffc0437232)
1732 drops at brk_limit+369bd232 (0xffffffffc0437232)
1 drops at brk_limit+369bd232 (0xffffffffc0437232)
1783 drops at brk_limit+369bd232 (0xffffffffc0437232)
1834 drops at brk_limit+369bd232 (0xffffffffc0437232)
1882 drops at brk_limit+369bd232 (0xffffffffc0437232)
2 drops at brk_limit+369bd232 (0xffffffffc0437232)
1934 drops at brk_limit+369bd232 (0xffffffffc0437232)
1984 drops at brk_limit+369bd232 (0xffffffffc0437232)
2 drops at brk_limit+369bd232 (0xffffffffc0437232)
2036 drops at brk_limit+369bd232 (0xffffffffc0437232)
2087 drops at brk_limit+369bd232 (0xffffffffc0437232)
2135 drops at brk_limit+369bd232 (0xffffffffc0437232)
4 drops at brk_limit+369bd232 (0xffffffffc0437232)
2187 drops at brk_limit+369bd232 (0xffffffffc0437232)
2237 drops at brk_limit+369bd232 (0xffffffffc0437232)
2289 drops at brk_limit+369bd232 (0xffffffffc0437232)
2338 drops at brk_limit+369bd232 (0xffffffffc0437232)
2 drops at brk_limit+369bd232 (0xffffffffc0437232)
2390 drops at brk_limit+369bd232 (0xffffffffc0437232)
2439 drops at brk_limit+369bd232 (0xffffffffc0437232)
3 drops at brk_limit+369bd232 (0xffffffffc0437232)
2492 drops at brk_limit+369bd232 (0xffffffffc0437232)
2544 drops at brk_limit+369bd232 (0xffffffffc0437232)
2595 drops at brk_limit+369bd232 (0xffffffffc0437232)
2641 drops at brk_limit+369bd232 (0xffffffffc0437232)
2694 drops at brk_limit+369bd232 (0xffffffffc0437232)
2745 drops at brk_limit+369bd232 (0xffffffffc0437232)
2 drops at udp4_lib_rcv+b9 (0xffffffff88ab5139)
2795 drops at brk_limit+369bd232 (0xffffffffc0437232)
2846 drops at brk_limit+369bd232 (0xffffffffc0437232)
2898 drops at brk_limit+369bd232 (0xffffffffc0437232)
2949 drops at brk_limit+369bd232 (0xffffffffc0437232)
3000 drops at brk_limit+369bd232 (0xffffffffc0437232)
251 drops at __brk_limit+369bd232 (0xffffffffc0437232)
6 drops at icmp_rcv+125 (0xffffffff88aba7a5)**

网卡信息我看不懂这个现象，希望大家能帮我解决这个问题，谢谢！

标签： linuxsocketstcpudpkernel

解决方案

这是预期的行为。假设您发送一个 65,500 字节的数据报，而您的最大数据包大小为 1,500 字节。这意味着每个数据报需要 44 个数据包。现在说你的丢包率是 1%。这意味着您的数据报丢失率为 35%。哎哟。

不要使用这么大的数据报。或者不要使用UDP。

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