Linux 网卡性能优化设置

在高速网络传输中，每秒传输的数据量非常大。网络设备设置有一种缓存机制，即“缓存区”，在 Linux 系统中，网卡缓冲分为两种类型：软件缓冲区和硬件缓冲区。
要提高网络吞吐率，首先当然是升级linux kernel。其次是设置linux系统参数和网卡驱动参数。
查看当前linux系统参数
$ cat /etc/sysctl.conf 
    vm.swappiness = 0
    net.ipv4.neigh.default.gc_stale_time = 120

    # see details in https://help.aliyun.com/knowledge_detail/39428.html
    net.ipv4.conf.all.rp_filter = 0
    net.ipv4.conf.default.rp_filter = 0
    net.ipv4.conf.default.arp_announce = 2
    net.ipv4.conf.lo.arp_announce = 2
    net.ipv4.conf.all.arp_announce = 2

    # see details in https://help.aliyun.com/knowledge_detail/41334.html
    net.ipv4.tcp_max_tw_buckets = 5000
    net.ipv4.tcp_syncookies = 1
    net.ipv4.tcp_max_syn_backlog = 1024
    net.ipv4.tcp_synack_retries = 2

    net.ipv6.conf.all.disable_ipv6 = 1
    net.ipv6.conf.default.disable_ipv6 = 1
    net.ipv6.conf.lo.disable_ipv6 = 1

    kernel.sysrq = 1

可以设置为下面这一组优化后的系统参数：
    sysctl -w net.ipv4.tcp_tw_reuse=1
    sysctl -w net.ipv4.tcp_tw_recycle=1
    sysctl -w net.ipv4.tcp_fin_timeout=30
    sysctl -w net.ipv4.tcp_keepalive_time=600
    sysctl -w net.ipv4.tcp_max_syn_backlog=8192
    sysctl -w net.ipv4.tcp_max_tw_buckets=5000
    sysctl -w net.ipv4.ip_local_port_range='1024 65000'
    sysctl -w net.ipv4.tcp_rmem='4096 436600 873200'
    sysctl -w net.ipv6.conf.all.disable_ipv6=1
    sysctl -w net.ipv6.conf.default.disable_ipv6=1
    sysctl -w net.ipv4.tcp_synack_retries=2
    sysctl -w net.ipv4.tcp_syn_retries=2

    sysctl -w net.core.wmem_max=16777216
    sysctl -w net.core.wmem_default=16777216
    sysctl -w net.core.rmem_max=16777216
    sysctl -w net.core.rmem_default=16777216

    $ sysctl -p

网卡驱动一般情况下不允许设置，但可以查询设置情况和统计信息以定位问题。
如果可能，应该升级linux kernel和net driver(ko)以便获得更好的网络性能。
下面是一台典型centos7 VPS的网卡信息，驱动较为简单。
root@iZj6c591g5r6irirqvcj5gZ ~/$ ethtool -i eth0
driver: virtio_net
version: 1.0.0
firmware-version: 
expansion-rom-version: 
bus-info: 0000:00:03.0
supports-statistics: no
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no
root@iZj6c591g5r6irirqvcj5gZ ~/$ ethtool -g eth0
Ring parameters for eth0:
Pre-set maximums:
RX:        4096
RX Mini:    0
RX Jumbo:    0
TX:        4096
Current hardware settings:
RX:        4096
RX Mini:    0
RX Jumbo:    0
TX:        4096

root@iZj6c591g5r6irirqvcj5gZ ~/$ ethtool -l eth0
Channel parameters for eth0:
Pre-set maximums:
RX:        0
TX:        0
Other:        0
Combined:    4
Current hardware settings:
RX:        0
TX:        0
Other:        0
Combined:    4

下面的设置全部失败。
root@iZj6c591g5r6irirqvcj5gZ ~/ $ 
$ ethtool -L eth0 tx 8 rx 8 other 8 combined 8
$ ethtool -G eth0 rx 8192 tx 8192
$ ethtool -C eth0 adaptive-tx off