Linux在4.9版本的内核新增了一款TCP拥塞控制技术：BBR，Linode最新内核也更新到4.9，但是没有把BBR编译进去，下面是教程是替换Linode CentOS7内核，并开启Google TCP-BBR优化算法方法。 1. 安装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
安装elrepo替换4.9内核及grub2 yum -y install kernel-ml grub2 查看4.9内核是否安装成功
[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. 替换Linde CentOS7内核
[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
点击Linode后台面板Dashboard，点击Edit按钮：  在Kernel下拉菜单，选择GRUB 2启动：  重启服务器： reboot 查看内核版本
[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. 开启TCP-BBR
cat >>/etc/sysctl.conf << EOF
net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr
EOF
内核参数生效： 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
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