需要更换内核，目前内核是测试版本

Centos6
http://elrepo.org/people/ajb/devel/kernel-ml/el6/x86_64/RPMS/
Centos7
http://elrepo.org/people/ajb/devel/kernel-ml/el7/x86_64/RPMS/

洛杉矶VPS测试CENTOS7

	








	rpm -ivh http://elrepo.org/people/ajb/devel/kernel-ml/el7/x86_64/RPMS/kernel-ml-4.9.0-0.rc8.el7.elrepo.x86_64.rpm --force 

grub2-set-default 'CentOS Linux (4.9.0-0.rc8.el7.elrepo.x86_64) 7 (Core)'

grub2-editenv list   #当前启动项

reboot

	echo "net.core.default_qdisc=fq" >> /etc/sysctl.conf 



	echo "net.ipv4.tcp_congestion_control=bbr" >> /etc/sysctl.conf 

sysctl -p

查看sysctl net.ipv4.tcp_available_congestion_control
lsmod | grep bbr 

以上是测试版 已经无效了，下面是正式版

http://elrepo.org/linux/kernel/el7/x86_64/RPMS/

http://elrepo.org/linux/kernel/el7/x86_64/RPMS/kernel-ml-4.9.0-1.el7.elrepo.x86_64.rpm

 
rpm -ivh http://elrepo.org/linux/kernel/el7/x86_64/RPMS/kernel-ml-4.9.0-1.el7.elrepo.x86_64.rpm --force 

grub2-set-default 'CentOS Linux (4.9.0-1.el7.elrepo.x86_64) 7 (Core)'

grub2-editenv list   #当前启动项

reboot

echo "net.core.default_qdisc=fq" >> /etc/sysctl.conf

echo "net.ipv4.tcp_congestion_control=bbr" >> /etc/sysctl.conf
sysctl -p

查看sysctl net.ipv4.tcp_available_congestion_control

lsmod | grep bbr 

以上不用看了
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org

rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm

yum --enablerepo=elrepo-kernel install kernel-ml

#查看内核
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
#设置内核
grub2-set-default 0
reboot
nano /etc/sysctl.conf

net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

sysctl -p
#查看生效
lsmod | grep bbr

#删除旧的内核
rpm -qa | grep kernel
yum autoremove kernel-3.10.0-327.13.1.el7.x86_64 

或者使用一键更换内核
wget --no-check-certificate https://github.com/teddysun/across/raw/master/bbr.sh && chmod +x bbr.sh && ./bbr.sh
CentOS使用yum update更新时不升级内核           
cp /etc/yum.conf    /etc/yum.conf.bak
nano /etc/yum.conf  在[main]的最后添加
exclude=kernel*

不能加exclude=centos-release*  不然无效