分类 Linux 下的文章

How to Deploy Google BBR on CentOS 7 in GCP

BBR (Bottleneck Bandwidth and RTT) is a new congestion control algorithm which is contributed to the Linux kernel TCP stack by Google. With BBR in place, a Linux server can get significantly increased throughput and reduced latency for connections. Besides, it's easy to deploy BBR because this algorithm requires only updates on the sender side, not in the network or on the receiver side.

In this article, I will show you how to deploy BBR on a Vultr CentOS 7 KVM server instance.

Prerequisites

A Vultr CentOS 7 x64 server instance.
A sudo user.

Step 1: Upgrade the kernel using the ELRepo RPM repository

In order to use BBR, you need to upgrade the kernel of your CentOS 7 machine to 4.9.0. You can easily get that done using the ELRepo RPM repository.

Before the upgrade, you can take a look at the current kernel:

uname -r
This command should output a string which resembles:

3.10.0-514.2.2.el7.x86_64
As you see, the current kernel is 3.10.0.

Install the ELRepo repo:

**sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sudo rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm**
Install the 4.9.0 kernel using the ELRepo repo:

sudo yum --enablerepo=elrepo-kernel install kernel-ml -y
Confirm the result:

rpm -qa | grep kernel
If the installation is successful, you should see kernel-ml-4.9.0-1.el7.elrepo.x86_64 among the output list:

kernel-ml-4.9.0-1.el7.elrepo.x86_64
kernel-3.10.0-514.el7.x86_64
kernel-tools-libs-3.10.0-514.2.2.el7.x86_64
kernel-tools-3.10.0-514.2.2.el7.x86_64
kernel-3.10.0-514.2.2.el7.x86_64
Now, you need to enable the 4.9.0 kernel by setting up the default grub2 boot entry.

Show all entries in the grub2 menu:

sudo egrep ^menuentry /etc/grub2.cfg | cut -f 2 -d \'
The result should resemble:

CentOS Linux 7 Rescue a0cbf86a6ef1416a8812657bb4f2b860 (4.9.0-1.el7.elrepo.x86_64)
CentOS Linux (4.9.0-1.el7.elrepo.x86_64) 7 (Core)
CentOS Linux (3.10.0-514.2.2.el7.x86_64) 7 (Core)
CentOS Linux (3.10.0-514.el7.x86_64) 7 (Core)
CentOS Linux (0-rescue-bf94f46c6bd04792a6a42c91bae645f7) 7 (Core)
Since the line count starts at 0 and the 4.9.0 kernel entry is on the second line, set the default boot entry as 1:

sudo grub2-set-default 1
Reboot the system:

sudo shutdown -r now
When the server is back online, log back in and rerun the uname command to confirm that you are using the correct Kernel:

uname -r
You should see the result as below:

4.9.0-1.el7.elrepo.x86_64

Step 2: Enable BBR

In order to enable the BBR algorithm, you need to modify the sysctl configuration as follows:

**echo 'net.core.default_qdisc=fq' | sudo tee -a /etc/sysctl.conf
echo 'net.ipv4.tcp_congestion_control=bbr' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p**
Now, you can use the following commands to confirm that BBR is enabled:

sudo sysctl net.ipv4.tcp_available_congestion_control
The output should resemble:

net.ipv4.tcp_available_congestion_control = bbr cubic reno
Next, verify with:

sudo sysctl -n net.ipv4.tcp_congestion_control
The output should be:

bbr
Finally, check that the kernel module was loaded:

lsmod | grep bbr
The output will be similar to:

tcp_bbr 16384 0

Step 3 (optional): Test the network performance enhancement

In order to test BBR's network performance enhancement, you can create a file in the web server directory for download, and then test the download speed from a web browser on your desktop machine.

**sudo yum install httpd -y
sudo systemctl start httpd.service
sudo firewall-cmd --zone=public --permanent --add-service=http
sudo firewall-cmd --reload
cd /var/www/html
sudo dd if=/dev/zero of=500mb.zip bs=1024k count=500**
Finally, visit the URL http://[your-server-IP]/500mb.zip from a web browser on your desktop computer, and then evaluate download speed.

That's all. Thank you for reading.

How to Deploy Google BBR on CentOS 6 in GCP

BBR (Bottleneck Bandwidth and RTT) is a new congestion control algorithm which is contributed to the Linux kernel TCP stack by Google. With BBR in place, a Linux server can get significantly increased throughput and reduced latency for connections. Besides, it's easy to deploy BBR because this algorithm requires only updates on the sender side, not in the network or on the receiver side.

In this article, I will show you how to deploy BBR on a Vultr CentOS 7 KVM server instance.

Prerequisites

A Vultr CentOS 6 x64 server instance.
A sudo user.

Step 1: Upgrade the kernel using the ELRepo RPM repository

In order to use BBR, you need to upgrade the kernel of your CentOS 7 machine to 4.9.0. You can easily get that done using the ELRepo RPM repository.

Before the upgrade, you can take a look at the current kernel:

uname -r
This command should output a string which resembles:

2.6.32-642.15.1.el6.x86_64
As you see, the current kernel is 2.6.32.

Install the ELRepo repo:

sudo rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
sudo rpm -Uvh http://www.elrepo.org/elrepo-release-6-6.el6.elrepo.noarch.rpm
Install the 4.10.4 kernel using the ELRepo repo:

sudo yum --enablerepo=elrepo-kernel install kernel-ml -y
Confirm the result:

rpm -qa | grep kernel
If the installation is successful, you should see kernel-ml-4.10.4-1.el6.elrepo.x86_64 among the output list:

dracut-kernel-004-409.el6_8.2.noarch
kernel-2.6.32-573.el6.x86_64
kernel-ml-4.10.4-1.el6.elrepo.x86_64
kernel-headers-2.6.32-642.15.1.el6.x86_64
abrt-addon-kerneloops-2.0.8-40.el6.centos.x86_64
kernel-2.6.32-642.15.1.el6.x86_64
kernel-firmware-2.6.32-642.15.1.el6.noarch
libreport-plugin-kerneloops-2.0.9-32.el6.centos.x86_6

Now, you need to enable the 4.10.4 kernel by setting up the default grub boot entry.

Show all entries in the grub2 menu:

sudo sed -i 's:default=.*:default=0:g' /etc/grub.conf

Reboot the system:

sudo shutdown -r now
When the server is back online, log back in and rerun the uname command to confirm that you are using the correct Kernel:

uname -r
You should see the result as below:

4.10.4-1.el6.elrepo.x86_64

Step 2: Enable BBR

In order to enable the BBR algorithm, you need to modify the sysctl configuration as follows:

echo 'net.core.default_qdisc=fq' | sudo tee -a /etc/sysctl.conf
echo 'net.ipv4.tcp_congestion_control=bbr' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p
Now, you can use the following commands to confirm that BBR is enabled:

sudo sysctl net.ipv4.tcp_available_congestion_control
The output should resemble:

net.ipv4.tcp_available_congestion_control = bbr cubic reno
Next, verify with:

sudo sysctl -n net.ipv4.tcp_congestion_control
The output should be:

bbr
Finally, check that the kernel module was loaded:

lsmod | grep bbr
The output will be similar to:

tcp_bbr 16384 0

Step 3 (optional): Test the network performance enhancement

In order to test BBR's network performance enhancement, you can create a file in the web server directory for download, and then test the download speed from a web browser on your desktop machine.

sudo yum install httpd -y
sudo server httpd start
cd /var/www/html
sudo dd if=/dev/zero of=500mb.zip bs=1024k count=500
Finally, visit the URL http://[your-server-IP]/500mb.zip from a web browser on your desktop computer, and then evaluate download speed.

That's all. Thank you for reading.

将程序从windows移植到linux(信号量和事件)

关于复杂的多线程和多进程应用程序的映射指南
随着开发人员将一些普及的 Windows® 应用程序迁移到 Linux™ 平台,企业中正在进行的向开放源码迁移的浪潮有可能引发极大的移植问题。这个由三部分组成的系列文章提供了一个映射指南,并附有一些例子,以简化从 Windows 到 Linux 的转移。本文是系列文章的第 2 部分,将介绍两种同步对象类型:信号量和事件。

- 阅读剩余部分 -

rhel 7使用unbound部署ddns

1、首先第一步安装,我这里已经安装过了
[root@colourstek wangmin]# yum install unbound
Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
Package unbound-1.4.20-26.el7.x86_64 already installed and latest version
Nothing to do
[root@colourstek wangmin]# systemctl restart unbound //启动DNS服务
[root@colourstek wangmin]# systemctl enable unbound //开机自动启动DNS服务
ln -s ‘/usr/lib/systemd/system/unbound.service‘ ‘/etc/systemd/system/multi-user.target.wants/unbound.service‘

2、修改配置文件
unbound安装好之后,默认配置文件地址为/etc/unbound/unbound.conf
贴上我的配置文件,加粗部分为我的修改
dns1.jpg
dns2.jpg
dns3.jpg
dns4.jpg
dns5.jpg
dns6.jpg
dns7.jpg
dns8.jpg
3、验证
[root@colourstek wangmin]# unbound-checkconf
[1476341835] unbound-checkconf[176447:0] warning: root hints /etc/unbound/root.hints: no NS content
unbound-checkconf: no errors in /etc/unbound/unbound.conf

4、重启unbound服务,如果防火墙是开的最好关掉
[root@colourstek wangmin]# systemctl restart unbound