How to Limit CPU and Memory Usage in Docker Containers
Isolate processes and guarantee resources with Docker containers
Introduction
Docker containers are a great way to isolate processes from each other on a single host. This can be especially useful when running multiple processes that are CPU or memory intensive, as it ensures that one process cannot starve the others of resources.
It is also possible to limit the amount of CPU or memory that a Docker container can use. This can be useful to prevent a single process from using too much of the host's resources or to guarantee that a container always has a minimum amount of resources available to it.
CPU Limits
CPU limits can be set using the --cpu-period and --cpu-quota parameters. The --cpu-period parameter sets the length of a CPU cycle in microseconds. The --cpu-quota parameter sets the number of cycles that a container is allowed to use in that period.
For example, to limit a container to using no more than 50% of a single CPU core, you would use the following parameters:
--cpu-period=50000
--cpu-quota=25000
You can also use the --cpus parameter to set the maximum number of CPUs that a container can use. For example, to limit a container to using two CPUs, you would use the following parameter:
--cpus=2
Memory Limits
Memory limits can be set using the --memory parameter. This parameter sets the maximum amount of memory that a container can use, in bytes.
For example, to limit a container to using no more than 512 MB of memory, you would use the following parameter:
--memory=512m
You can also use the --memory-swap parameter to set the maximum amount of memory and swap that a container can use. This parameter is set in the same way as the --memory parameter, in bytes.
For example, to limit a container to using no more than 512 MB of memory and swap, you would use the following parameter:
--memory-swap=512m
Example Docker command:
docker run --name my-container --cpu-period=50000 --cpu-quota=25000 --memory=512m my-image
Example docker-compose configuration:
version: '3'
services:
my-service:
image: my-image
cpu_period: 50000
cpu_quota: 25000
memory: 512m
Conclusion
Docker containers are a great way to isolate processes from each other on a single host. CPU and memory limits can be set to ensure that one process cannot starve the others of resources or to guarantee that a container always has a minimum amount of resources available to it.
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