在使用linux的centos7.4遇到的各種坑，其中一個項目採用四層架構，配置層，平臺層，邏輯服務器管理層和集體邏輯服務器層的，一個整體的遊戲項目，其中，作為整個項目負責人和架構打架著，項目運行一年來，遇到了各種各樣怪異的問題。其中就是tcp緩存區堵塞的問題，剛開始時候，以為是代碼問題，花了半年的時間來排除，驗證，把能想到的問題都做了一個遍，問題還是存在。最後應該幾個調優和驗證。附上算比較穩定centos7.4的內核調優詳細參數如下：
內核配置文件：/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
# 參數的值決定了內核放棄鏈接之前發送SYN+ACK包的數量，該參數對應系統路徑為：/proc/sys/net/ipv4/tcp_synack_retries，默認是2
net.ipv4.tcp_synack_retries=3
# 表示內核放棄建立鏈接之前發送SYN包的數量，該參數對應系統路徑為：/proc/sys/net/ipv4/tcp_syn_retries，默認是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
#設置最大內存共享段大小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
# 開啟SYN洪水攻擊保護
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
#避免放大攻擊
net.ipv4.icmp_echo_ignore_broadcasts=1
#關閉ipv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
# 開啟惡意icmp錯誤消息保護
net.ipv4.icmp_ignore_bogus_error_responses = 1
#關閉路由轉發
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
#開啟反向路徑過濾
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
#處理無源路由的包
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
#關閉sysrq功能
kernel.sysrq = 0
#每個網絡接口接收數據包的速率比內核處理這些包的速率快時，允許送到隊列的數據包的最大數目
net.core.netdev_max_backlog = 262144
#限制僅僅是為了防止簡單的DoS 攻擊
net.ipv4.tcp_max_orphans = 3276800
# 確保無人能修改路由表
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
#決定檢查過期多久鄰居條目
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解決ARP映射問題
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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