The benefits of jemalloc versus glibc memory allocator for use with MySQL have been widely discussed. With jemalloc (along with Transparent Huge Pages disabled) there is less memory fragmentation, and thus more efficient resource management of the server memory. For MySQL 5.6, installing jemalloc is enough to enable it when starting the MySQL process. However, for MySQL 5.7 and 8.0.X series, you will need to take a few extra steps.
Enabling jemalloc on Percona Server for MySQL
Installing the jemalloc package is simple for Percona. This is because the library is available on the Percona repository, which is available for both apt and yum package management:
- Installing Percona Server for MySQL on Debian and Ubuntu
- Installing Percona Server for MySQL on Red Hat Enterprise Linux and CentOS
Once you have the repo, just run the install command (according to your OS) to install it:
Now that the package is installed, we need to make MySQL working with it. And now, it depends on how you are starting MySQL:
yum install jemalloc / apt-get install libjemalloc1
Using systemd Services (systemctl Command)
# cat /etc/sysconfig/mysql LD_PRELOAD=/usr/lib64/libjemalloc.so.1
2-) Start MySQL
systemctl start mysql
Starting Manually
If you are starting it manually, in the command line, you need to specify the library in the LD_PRELOAD. So the command to initialize will be similar to this one:
LD_PRELOAD=/usr/lib64/libjemalloc.so.1 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid --user mysql
Check if MySQL is Using jemalloc
pt-mysql-summary which is part of the Percona Toolkit:[root@localhost ~]# pt-mysql-summary | grep -A5 -i "memory management" # Memory management library ################################## jemalloc enabled in mysql config for process with id 14490 Using jemalloc from /usr/lib64/libjemalloc.so.1 # The End ####################################################
And you can also do it manually:
pid=$(pidof mysqld)
cat /proc/${pid}/environ
Or:
lsof -Pn -p $(pidof mysqld) | grep jemalloc
Conclusion
This blog post was written to update the guidelines of jemalloc. Important to mention that using the recommendations above regarding systemd, the changes will persist across MySQL upgrades.
Finally, jemalloc still is a good memory allocator and I consider it part of the best practices that should be implemented before the deployment in production.
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