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设置推荐值基本原理
net.core.netdev_max_backlog30000Set maximum number of packets, queued on the INPUT side, when the interface receives packets faster than kernel can process them. Recommended setting is for 10GbE links. For 1GbE links use 设置包的最大数, 在输入端进行排队, 当接口接收包比内核处理更快时. 推荐设置为10GbE 链路. 对于1GbE 链路使用 8000.
net.core.wmem_max67108864Set max to 对于 1GbE 链路, 设置最大数为 16MB (16777216) for 1GbE links and , 而对于10GbE链路为 64MB (67108864) for 10GbE links.
net.core.rmem_max67108864Set max to 对于 1GbE 链路, 设置最大数为 16MB (16777216) for 1GbE links and , 而对于10GbE链路为 64MB (67108864) for 10GbE links.
net.ipv4.tcp_congestion_controlhtcpThere seem to be bugs in both bic and cubic (the default) for a number of versions of the Linux kernel up to version 这看起来是 bugs 在 bic 和 cubic 上(默认) , 对于 Linux 内核上到版本 2.6.33. The kernel version for Redhat 5.x is 内核版本是 2.6.18-x and , Redhat 6.x内核版本是 2.6.32-x for Redhat 6.x
net.ipv4.tcp_congestion_window10This is the default for Linux operating systems based on 默认情况下, Linux OS 是基于 Linux kernel 2.6.39 or later或以上版本.
net.ipv4.tcp_fin_timeout10This setting determines the time that must elapse before TCP/IP can release a closed connection and reuse its resources. During this TIME_WAIT state, reopening the connection to the client costs less than establishing a new connection. By reducing the value of this entry, TCP/IP can release closed connections faster, making more resources available for new connections. The default value is 60. The recommened setting lowers its to 10. You can lower this even further, but too low, and you can run into socket close errors in networks with lots of jitter.
net.ipv4.tcp_keepalive_interval30This determines the wait time between isAlive interval probes. Default value is 75. Recommended value reduces this in keeping with the reduction of the overall keepalive time.
net.ipv4.tcp_keepalive_probes5How many keepalive probes to send out before the socket is timed out. Default value is 9. Recommended value reduces this to 5 so that retry attempts will take 2.5 minutes.
net.ipv4.tcp_keepalive_time600Set the TCP Socket timeout value to 10 minutes instead of 2 hour default. With an idle socket, the system will wait tcp_keepalive_time seconds, and after that try tcp_keepalive_probes times to send a TCP KEEPALIVE in intervals of tcp_keepalive_intvl seconds. If the retry attempts fail, the socket times out.
net.ipv4.tcp_low_latency1Configure 配置 TCP for low latency, favoring low latency over throughput为低延时, 在吞吐量上达到低延时
net.ipv4.tcp_max_orphans16384Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory
net.ipv4.tcp_max_tw_buckets1440000Maximal number of timewait sockets held by system simultaneously. If this number is exceeded time-wait socket is immediately destroyed and warning is printed. This limit exists to help prevent simple DoS attacks.
net.ipv4.tcp_no_metrics_save1Disable caching TCP metrics on connection close禁用 连接关闭的缓存TCP metrics
net.ipv4.tcp_orphan_retries0Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory
net.ipv4.tcp_rfc13371Enable a fix for RFC1337 - time-wait assassination hazards in TCP
net.ipv4.tcp_rmem10240 131072 33554432Setting is min/default/max. Recommed increasing the Linux autotuning TCP buffer limit to 32MB
net.ipv4.tcp_wmem10240 131072 33554432Setting is min/default/max. Recommed increasing the Linux autotuning TCP buffer limit to 32MB
net.ipv4.tcp_sack1启用 选择确认
net.ipv4.tcp_slow_start_after_idle0By default, TCP starts with a single small segment, gradually increasing it by one each time. This results in unnecessary slowness that impacts the start of every request.
net.ipv4.tcp_syncookies0Many default Linux installations use SYN cookies to protect the system against malicious attacks that flood TCP SYN packets. The use of SYN cookies dramatically reduces network bandwidth, and can be triggered by a running Geode cluster. If your Geode cluster is otherwise protected against such attacks, disable SYN cookies to ensure that Geode network throughput is not affected. 
NOTE: if SYN floods are an issue and SYN cookies can’t be disabled, try the following: 
net.ipv4.tcp_max_syn_backlog="16384"
net.ipv4.tcp_synack_retries="1" 
net.ipv4.tcp_max_orphans="400000"
net.ipv4.tcp_timestamps1Enable timestamps as defined in RFC1323:
net.ipv4.tcp_tw_recycle1This enables fast recycling of TIME_WAIT sockets. The default value is 0 (disabled). Should be used with caution with load balancers.
net.ipv4.tcp_tw_reuse1This allows reusing sockets in TIME_WAIT state for new connections when it is safe from protocol viewpoint. Default value is 0 (disabled). It is generally a safer alternative to tcp_tw_recycle. The tcp_tw_reuse setting is particularly useful in environments where numerous short connections are open and left in TIME_WAIT state, such as web servers and loadbalancers.
net.ipv4.tcp_window_scaling1Turn on window scaling which can be an option to enlarge the transfer window:

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