Configuring Linux for MariaDB
Contents
Linux kernel settings
IO scheduler
For optimal IO performance running a database we are using the none (previously called noop) scheduler. Recommended schedulers are none and mq-deadline (previously called deadline). You can check your scheduler setting with:
cat /sys/block/${DEVICE}/queue/scheduler
For instance, it should look like this output:
cat /sys/block/vdb/queue/scheduler [none] mq-deadline kyber bfq
Older kernels may look like:
cat /sys/block/sda/queue/scheduler [noop] deadline cfq
Writing the new scheduler name to the same /sys node will change the scheduler:
echo mq-deadline > /sys/block/vdb/queue/scheduler
The impact of schedulers depend significantly on workload and hardware. You can measure the IO-latency using the biolatency bcc-tools script with an aim to keep the mean as low as possible.
Resource Limits
Configuring the Open Files Limit
By default, the system limits how many open file descriptors a process can have open at one time. It has both a soft and hard limit. On many systems, both the soft and hard limit default to 1024. On an active database server, it is very easy to exceed 1024 open file descriptors. Therefore, you may need to increase the soft and hard limits. There are a few ways to do so.
If you are using mysqld_safe or mariadbd-safe to start mysqld, then see the instructions at mariadbd-safe: Configuring the Open Files Limit.
If you are using systemd to start mysqld, then see the instructions at systemd: Configuring the Open Files Limit.
Otherwise, you can set the soft and hard limits for the mysql user account by adding the following lines to /etc/security/limits.conf:
mysql soft nofile 65535 mysql hard nofile 65535
After the system is rebooted, the mysql user should use the new limits, and the user's ulimit output should look like the following:
$ ulimit -Sn 65535 $ ulimit -Hn 65535
Configuring the Core File Size
By default, the system limits the size of core files that could be created. It has both a soft and hard limit. On many systems, the soft limit defaults to 0. If you want to enable core dumps, then you may need to increase this. Therefore, you may need to increase the soft and hard limits. There are a few ways to do so.
If you are using mysqld_safe or mariadbd-safe to start mysqld, then see the instructions at mariadb-safe: Configuring the Core File Size.
If you are using systemd to start mysqld, then see the instructions at systemd: Configuring the Core File Size.
Otherwise, you can set the soft and hard limits for the mysql user account by adding the following lines to /etc/security/limits.conf:
mysql soft core unlimited mysql hard core unlimited
After the system is rebooted, the mysql user should use the new limits, and the user's ulimit output should look like the following:
$ ulimit -Sc unlimited $ ulimit -Hc unlimited
