在使用linux的centos7.4遇到的各种坑，其中一个项目采用四层架构，配置层，平台层，逻辑服务器管理层和集体逻辑服务器层的，一个整体的游戏项目，其中，作为整个项目负责人和架构打架着，项目运行一年来，遇到了各种各样怪异的问题。其中就是tcp缓存区堵塞的问题，刚开始时候，以为是代码问题，花了半年的时间来排除，验证，把能想到的问题都做了一个遍，问题还是存在。最后应该几个调优和验证。附上算比较稳定centos7.4的内核调优详细参数如下：
内核配置文件：/etc/sysctl.conf
net.ipv4.tcp_mem = 768432 2097152 15242880
net.ipv4.tcp_wmem = 40960 163840 4194304
net.ipv4.tcp_rmem = 40960 873800 4194304
#net.core.somaxconn=6553600
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 524288000
net.core.wmem_max = 524288000
net.ipv4.tcp_syncookies=1
net.ipv4.tcp_max_syn_backlog=81920
net.ipv4.tcp_timestamps=0
# 参数的值决定了内核放弃链接之前发送SYN+ACK包的数量，该参数对应系统路径为：/proc/sys/net/ipv4/tcp_synack_retries，默认是2
net.ipv4.tcp_synack_retries=3
# 表示内核放弃建立链接之前发送SYN包的数量，该参数对应系统路径为：/proc/sys/net/ipv4/tcp_syn_retries，默认是6
net.ipv4.tcp_syn_retries=3
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 300
net.ipv4.ip_local_port_range = 20000 65000
net.ipv4.tcp_max_tw_buckets = 6000
net.ipv4.route.max_size = 5242880
kernel.sem=250 65536 100 2048
kernel.msgmnb = 4203520
kernel.msgmni = 64
kernel.msgmax = 65535
#设置最大内存共享段大小bytes
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
kernel.shmmni = 655360
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_no_metrics_save=1
# 开启SYN洪水攻击保护
kernel.core_uses_pid = 1
net.ipv4.conf.lo.arp_announce=2
net.ipv4.tcp_sack = 1
kernel.randomize_va_space=1
net.nf_conntrack_max = 25000000
net.netfilter.nf_conntrack_max = 25000000
net.netfilter.nf_conntrack_tcp_timeout_established = 180
#net.ipv4.netfilter.ip_conntrack_max=1000000
net.netfilter.nf_conntrack_tcp_timeout_time_wait = 120
net.netfilter.nf_conntrack_tcp_timeout_close_wait = 60
net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 120
#避免放大攻击
net.ipv4.icmp_echo_ignore_broadcasts=1
#关闭ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
# 开启恶意icmp错误消息保护
net.ipv4.icmp_ignore_bogus_error_responses = 1
#关闭路由转发
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
#开启反向路径过滤
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
#处理无源路由的包
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
#关闭sysrq功能
kernel.sysrq = 0
#每个网络接口接收数据包的速率比内核处理这些包的速率快时，允许送到队列的数据包的最大数目
net.core.netdev_max_backlog = 262144
#限制仅仅是为了防止简单的DoS 攻击
net.ipv4.tcp_max_orphans = 3276800
# 确保无人能修改路由表
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
vm.swappiness = 0
#决定检查过期多久邻居条目
net.ipv4.neigh.default.gc_stale_time=120
fs.file-max = 40000500
fs.nr_open = 40000500
kernel.perf_cpu_time_max_percent=60
kernel.perf_event_max_sample_rate=6250
kernel.sched_migration_cost_ns=5000000
net.core.optmem_max= 25165824
vm.max_map_count=262144
net.core.somaxconn = 65535
#使用arp_announce / arp_ignore解决ARP映射问题
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.all.arp_announce=2
net.ipv4.conf.lo.arp_announce=2
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