Linode CentOS7開啟Google TCP-BBR優化算法

Linux在4.9版本的內核新增了一款TCP擁塞控制技術：BBR，Linode最新內核也更新到4.9，但是沒有把BBR編譯進去，下面是教程是替換Linode CentOS7內核，並開啟Google TCP-BBR優化算法方法。

1. 安裝elrepo提供的kernel4.9

增加elrepo源

cat > /etc/yum.repos.d/elrepo.repo << EOF
[elrepo-kernel]
baseurl=http://elrepo.org/linux/kernel/el7/\$basearch/
        http://mirrors.coreix.net/elrepo/kernel/el7/\$basearch/
        http://jur-linux.org/download/elrepo/kernel/el7/\$basearch/
        http://repos.lax-noc.com/elrepo/kernel/el7/\$basearch/
        http://mirror.ventraip.net.au/elrepo/kernel/el7/\$basearch/
enabled=1
gpgcheck=0
EOF

安裝elrepo替換4.9內核及grub2

yum -y install kernel-ml grub2

查看4.9內核是否安裝成功

[root@linode1495332 ~]# ls -l /boot/vmlinuz*
-rwxr-xr-x 1 root root 6037696 Dec 22 10:16 /boot/vmlinuz-0-rescue-72863e389b584a4dab36fae7f3bffda2
-rwxr-xr-x 1 root root 6037696 Dec 12 05:37 /boot/vmlinuz-4.9.0-1.el7.elrepo.x86_64

2. 替換Linde CentOS7內核

[root@linode1495332 etc]# mkdir /boot/grub
[root@linode1495332 etc]# grub2-mkconfig -o /boot/grub/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.9.0-1.el7.elrepo.x86_64
Found initrd image: /boot/initramfs-4.9.0-1.el7.elrepo.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-72863e389b584a4dab36fae7f3bffda2
Found initrd image: /boot/initramfs-0-rescue-72863e389b584a4dab36fae7f3bffda2.img
done

點擊Linode後台面板Dashboard，點擊Edit按鈕：

在Kernel下拉菜單，選擇GRUB 2啟動：

重啟服務器：

reboot

查看內核版本

[root@linode1495332 ~]# uname -a
Linux linode1495332.members.linode.com 4.9.0-1.el7.elrepo.x86_64 #1 SMP Sun Dec 11 15:43:54 EST 2016 x86_64 x86_64 x86_64 GNU/Linux

3. 開啟TCP-BBR

cat >>/etc/sysctl.conf << EOF
net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr
EOF

內核參數生效：

sysctl -p

查看bbr是否生效：

[root@linode1495332 ~]# sysctl net.ipv4.tcp_available_congestion_control
net.ipv4.tcp_available_congestion_control = bbr cubic reno
[root@linode1495332 ~]# lsmod | grep bbr
tcp_bbr                16384  70