Detailed explanation of solving the problem of memory exhaustion caused by too many php-fpm processes under Linux

This article mainly introduces how to solve the problem of memory exhaustion caused by too many php-fpm processes under Linux. Friends who need it can refer to it

Recently, I found that the Linux server and database service of my personal blog often hang up. , which resulted in the need to restart before I could access it normally, which was extremely disgusting, so I decided to start solving the problem and free up my time and energy (I didn’t want to have problems frequently and then restart manually, which was laborious and time-consuming).

Analyze the problem

After discovering the problem, first use the free -m command to check the current server execution status:

You can see that my server memory is 2G, but currently there is only 70M of available memory left, and the memory usage is as high as 92%. It is very likely that the memory usage is too high. The database service hangs up.

Continue to see the details, use the top command:

Then look at the process details listed in the command output, Focus on the memory usage ratio in column 10:

It is found that the CPU usage is not high, and the CPU problem is also ruled out. In addition, you can see that the database service takes up 15.2%. Memory, when the memory usage is too high, it will crowd out the database process (the process that takes up the most memory), causing the service to hang up, so we need to check the detailed memory usage. Which processes consume so much memory?

Use command:

ps auxw|head -1;ps auxw|sort -rn -k4|head -40

View the top 40 processes that consume the most memory:

Looking at the memory usage ratio in the fourth column, we found that in addition to the mysql database service, the php-fpm service pool opened too many sub-processes, occupying more than half of the memory. The problem was found, and we started to solve the problem: setting control php- Number of fpm process pool processes.

Solve the problem

Through various search methods, I found that you can control php- by configuring the pm.max_children attribute. Number of fpm child processes. First, open the php-fpm configuration file and execute the command:

vi /etc/php-fpm.d/www.conf

Find the pm.max_children field and discover its The value is too large:

As shown in the figure, the value of pm.max_children is 50. Each process occupies 1%-2.5% of the memory, which adds up to It consumes most of the memory, so we need to reduce its value. The blogger here sets it to 25. At the same time, check the following two attributes:

pm.max_spare_servers: This value means Guarantee the maximum number of idle processes. If the idle processes are greater than this value, clean them up pm.min_spare_servers: Guarantee the minimum number of idle processes. If the idle processes are less than this value, create a new child process;

Neither of these two values ​​can be greater than the pm.max_children value. Usually, the pm.max_spare_servers value is set to 60% of the pm.max_children value - 80%.

Finally, restart php-fpm

systemctl restart php-fpm

Check the memory usage again, the memory usage is reduced a lot:

After observing the memory usage many times, we found that after this improvement, the server memory resource consumption has been greatly alleviated.

ps: Check the number of processes started by php-fpm and the memory limit of each process

1. Use the command to check the total number of processes opened on the server. How many php-cgi processes are there

 ps -fe |grep "php-fpm"|grep "pool"|wc -l

2. Check how many php-cgi processes are used to handle tcp requests

 netstat -anp|grep "php-fpm"|grep "tcp"|grep "pool"|wc -l

3.In the linux nginx php environment, the memory limit of each php-fpm process

Setting method:

Edit the php-fpm.conf configuration file

php_admin_value[memory_limit] = 128M (the configuration file on my server is in /etc/php5/fpm/pool.d/www.conf This file is included in php-fpm.conf) The following numbers can be changed at will: 32M, 64M, 128M, 256M, 512M. This setting can be written according to your server memory size and your needs. After modification, Load the php-fpm service.

Summary

The above is the solution to the problem of memory exhaustion caused by too many php-fpm processes under Linux introduced by the editor. I hope it is helpful to you. If you have any questions, please leave me a message and I will reply to you in time. I would also like to thank you all for your support of the php Chinese website!

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