前言
K8S 性能优化系列文章，本文为第一篇：OS sysctl 性能优化参数最佳实践。
参数一览
sysctl 调优参数一览
# Kubernetes Settings
vm.max_map_count = 262144
kernel.softlockup_panic = 1
kernel.softlockup_all_cpu_backtrace = 1
net.ipv4.ip_local_reserved_ports = 30000-32767
# Increase the number of connections
net.core.somaxconn = 32768
# Maximum Socket Receive Buffer
net.core.rmem_max = 16777216
# Maximum Socket Send Buffer
net.core.wmem_max = 16777216
# Increase the maximum total buffer-space allocatable
net.ipv4.tcp_wmem = 4096 87380 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
# Increase the number of outstanding syn requests allowed
net.ipv4.tcp_max_syn_backlog = 8096
# For persistent HTTP connections
net.ipv4.tcp_slow_start_after_idle = 0
# Allow to reuse TIME_WAIT sockets for new connections
# when it is safe from protocol viewpoint
net.ipv4.tcp_tw_reuse = 1
# Max number of packets that can be queued on interface input
# If kernel is receiving packets faster than can be processed
# this queue increases
net.core.netdev_max_backlog = 16384
# Increase size of file handles and inode cache
fs.file-max = 2097152
# Max number of inotify instances and watches for a user
# Since dockerd runs as a single user, the default instances value of 128 per user is too low
# e.g. uses of inotify: nginx ingress controller, kubectl logs -f
fs.inotify.max_user_instances = 8192
fs.inotify.max_user_watches = 524288
# Additional sysctl flags that kubelet expects
vm.overcommit_memory = 1
kernel.panic = 10
kernel.panic_on_oops = 1
# Prevent docker from changing iptables: https://github.com/kubernetes/kubernetes/issues/40182
net.ipv4.ip_forward=1
如果是 AWS，额外增加如下：
# AWS settings
# Issue #23395
net.ipv4.neigh.default.gc_thresh1=0
如果启用了 IPv6，额外增加如下：
# Enable IPv6 forwarding for network plugins that don't do it themselves
net.ipv6.conf.all.forwarding=1
参数解释
| 分类 | 内核参数 | 说明 | 参考链接 |
|---|---|---|---|
| Kubernetes | vm.max_map_count = 262144 |
限制一个进程可以拥有的VMA(虚拟内存区域)的数量，<br />一个更大的值对于 elasticsearch、mongo 或其他 mmap 用户来说非常有用 | ES Configuration |
| Kubernetes | kernel.softlockup_panic = 1 |
用于解决 K8S 内核软锁相关 bug | root cause kernel soft lockups · Issue #37853 · kubernetes/kubernetes (github.com) |
| Kubernetes | kernel.softlockup_all_cpu_backtrace = 1 |
用于解决 K8S 内核软锁相关 bug | root cause kernel soft lockups · Issue #37853 · kubernetes/kubernetes (github.com) |
| Kubernetes | net.ipv4.ip_local_reserved_ports = 30000-32767 |
默认 K8S Nodport 端口 | service-node-port-range and ip_local_port_range collision · Issue #6342 · kubernetes/kops (github.com) |
| 网络 | net.core.somaxconn = 32768 |
表示socket监听（listen）的backlog上限。什么是backlog？backlog就是socket的监听队列，当一个请求（request）尚未被处理或建立时，他会进入backlog。<br />增加连接数. | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.core.rmem_max = 16777216 |
接收套接字缓冲区大小的最大值(以字节为单位)。<br />最大化 Socket Receive Buffer | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.core.wmem_max = 16777216 |
发送套接字缓冲区大小的最大值(以字节为单位)。<br />最大化 Socket Send Buffer | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.ipv4.tcp_wmem = 4096 87380 16777216<br />net.ipv4.tcp_rmem = 4096 87380 16777216 | 增加总的可分配的 buffer 空间的最大值 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.ipv4.tcp_max_syn_backlog = 8096 |
表示那些尚未收到客户端确认信息的连接（SYN消息）队列的长度，默认为1024<br />增加未完成的syn请求的数量 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.ipv4.tcp_slow_start_after_idle = 0 |
持久化 HTTP 连接 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.ipv4.tcp_tw_reuse = 1 |
表示允许重用TIME_WAIT状态的套接字用于新的TCP连接,默认为0，表示关闭。<br />允许在协议安全的情况下重用TIME_WAIT 套接字用于新的连接 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.core.netdev_max_backlog = 16384 |
当网卡接收数据包的速度大于内核处理的速度时，会有一个队列保存这些数据包。这个参数表示该队列的最大值<br />如果内核接收数据包的速度超过了可以处理的速度，这个队列就会增加 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 文件系统 | fs.file-max = 2097152 |
该参数决定了系统中所允许的文件句柄最大数目，文件句柄设置代表linux系统中可以打开的文件的数量。<br />增加文件句柄和inode缓存的大小 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 文件系统 | fs.inotify.max_user_instances = 8192<br />fs.inotify.max_user_watches = 524288 | 一个用户的inotify实例和watch的最大数量 由于dockerd作为单个用户运行，每个用户的默认实例值128太低了 例如使用inotify: nginx ingress controller, kubectl logs -f |
Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| kubelet | vm.overcommit_memory = 1 |
对内存分配的一种策略<br />=1， 表示内核允许分配所有的物理内存，而不管当前的内存状态如何 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| kubelet | kernel.panic = 10 |
panic错误中自动重启，等待时间为10秒 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| kubelet | kernel.panic_on_oops = 1 |
在Oops发生时会进行panic()操作 | Image: We should tweak our sysctls · Issue #261 · kubernetes-retired/kube-deploy (github.com) |
| 网络 | net.ipv4.ip_forward=1 |
启用ip转发<br />另外也防止docker改变iptables | Upgrading docker 1.13 on nodes causes outbound container traffic to stop working · Issue #40182 · kubernetes/kubernetes (github.com) |
| 网络 | net.ipv4.neigh.default.gc_thresh1=0 |
修复 AWS arp_cache: neighbor table overflow! 报错 |
arp_cache: neighbor table overflow! · Issue #4533 · kubernetes/kops (github.com) |
EOF
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