Linux BBR 实践

BBR 的作用就是加速 TCP，即：尽可能的充分利用带宽；降低 buffer 占用率，从而降低延迟。

Before

ubuntu@ip-x-x-x-x:/usr/local/bin$ sudo youtube-dl https://www.youtube.com/watch?v=4SdcmxGC3Yc&list=PLo7mBDsRHu11Szh1t-CRqwliRGRA1JOZJ&index=2
[1] 23958
[2] 23959
ubuntu@ip-x-x-x-x:/usr/local/bin$ WARNING: Assuming --restrict-filenames since file system encoding cannot encode all characters. Set the LC_ALL environment variable to fix this.
[youtube] 4SdcmxGC3Yc: Downloading webpage
[youtube] 4SdcmxGC3Yc: Downloading video info webpage
[youtube] 4SdcmxGC3Yc: Extracting video information
[youtube] 4SdcmxGC3Yc: Downloading MPD manifest
[youtube] 4SdcmxGC3Yc: Downloading MPD manifest
[download] Destination: Getting_started_webinar_-_February_2017-4SdcmxGC3Yc.mp4
[download] 100% of 171.28MiB in 00:40
[1]-  Done                    sudo youtube-dl https://www.youtube.com/watch?v=4SdcmxGC3Yc
[2]+  Done                    list=PLo7mBDsRHu11Szh1t-CRqwliRGRA1JOZJ

After

ubuntu@ip-x-x-x-x:/usr/local/bin$ sudo youtube-dl https://www.youtube.com/watch?v=4SdcmxGC3Yc&list=PLo7mBDsRHu11Szh1t-CRqwliRGRA1JOZJ&index=2
[1] 1945
[2] 1946
ubuntu@ip-x-x-x-x:/usr/local/bin$ WARNING: Assuming --restrict-filenames since file system encoding cannot encode all characters. Set the LC_ALL environment variable to fix this.
[youtube] 4SdcmxGC3Yc: Downloading webpage
[youtube] 4SdcmxGC3Yc: Downloading video info webpage
[youtube] 4SdcmxGC3Yc: Extracting video information
[youtube] 4SdcmxGC3Yc: Downloading MPD manifest
[youtube] 4SdcmxGC3Yc: Downloading MPD manifest
[download] Destination: Getting_started_webinar_-_February_2017-4SdcmxGC3Yc.mp4
[download] 100% of 171.28MiB in 00:08
[1]-  Done                    sudo youtube-dl https://www.youtube.com/watch?v=4SdcmxGC3Yc
[2]+  Done                    list=PLo7mBDsRHu11Szh1t-CRqwliRGRA1JOZJ

升级前

系统内核要求：Linux kernel 4.9 及以上

检查系统内核版本

uname -r

如果系统版本不满足要求，先升级内核：

在 内核下载地址：kernel.ubuntu 商业网/~kernel-ppa/mainline 里找到你要用的内核，即 4.9+ 版本。

另外你要注意：

如果系统是 64 位，则下载 amd64 的 linux-image 中含有 generic 这个 deb 包；

如果系统是 32 位，则下载 i386 的 linux-image 中含有 generic 这个 deb 包

这里我使用的是 4.10 版本：

sudo wget http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.10/linux-image-4.10.0-041000-generic_4.10.0-041000.201702191831_amd64.deb
sudo dpkg -i linux-image-4.10.0-041000-generic_4.10.0-041000.201702191831_amd64.deb
sudo update-grub
sudo reboot

安装（开启） BBR

echo "net.core.default_qdisc=fq" >> /etc/sysctl.conf  
echo "net.ipv4.tcp_congestion_control=bbr" >> /etc/sysctl.conf  
sysctl -p  # 立即生效配置

内核是否已开启 BBR

sysctl net.ipv4.tcp_available_congestion_control  
sysctl net.ipv4.tcp_congestion_control  

当前内核是否载入 tcp_bbr 模块

lsmod | grep bbr