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According to Docker documentation, in order to limit a container to a certain amount of cpu, we use the parameter --cpus when starting the container:
docker run -it --cpus=".5" ubuntu /bin/bash
Now that I have the container running, how do I check that limit that was assigned to the container in the first place?
In other words, is there a command that I can run and I can see that .5 that was assigned to the ubuntu container of the example?
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Run the docker stats command to display the status of your containers. Memory is listed under the MEM USAGE / LIMIT column. This provides a snapshot of how much memory the container is utilizing and what it's memory limit is. CPU utilization is listed under the CPU % column.
On windows, a container defaults to using two CPUs. If hyperthreading is available this is one core and two logical processors. If hyperthreading is not available this is two cores and two logical processors.
To control a container's CPU usage, you can use the --cpu-period and --cpu-quota options with the docker create and docker run commands from version 1.7. 0 of Docker onward.
Limit Docker Container CPU Usage You can also use the --cpu-shares option to give the container a greater or lesser proportion of CPU cycles. By default, this is set to 1024. To find more options for limiting container CPU usage, please refer to Docker's official documentation.
As soon as the second container appears, Docker starts balancing the CPU consumption based on values provided for --cpu-shares. Once the second container finished calculating square roots of random numbers, the first container will again consume 150%. Defining Docker container CPU limits is as essential as defining memory limits.
The following command will run the stress container for 20 seconds: # 20 seconds NO LIMIT docker run -d --rm progrium/stress -c 8 -t 20s The container allocates all of the available 200% CPU capacity (per CPU you have 100%) to get its job done. Now let’s limit the next container to just one (1) CPU.
As an example, for an Ubuntu container to have the memory reservation of 750 MB and the maximum RAM capacity of 1 BG, use the command: Just like RAM usage, Docker containers don’t have any default limitations for the host’s CPU. Giving containers unlimited CPU usage can lead to issues.
Run the docker stats command to display the status of your containers. Memory is listed under the MEM USAGE / LIMIT column. This provides a snapshot of how much memory the container is utilizing and what it’s memory limit is. CPU utilization is listed under the CPU % column. Network traffic is represented under the NET I/O column.
You can check the field NanoCpus in docker inspect command.
Specify how much of the available CPU resources a container can use. For instance, if the host machine has two CPUs and you set --cpus="1.5", the container is guaranteed at most one and a half of the CPUs. This is the equivalent of setting --cpu-period="100000" and --cpu-quota="150000". Available in Docker 1.13 and higher.
In your example, the NanoCpus should be 500000000 (0.5 * 100000 * 10000)
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The first command to check is docker container inspect.
docker container inspect <container ID or name>|grep -i cpu
With --format, you can even extract its value directly if exposed.
Then, at runtime, check docker stats to see if, at runtime, the percentage of the host’s CPU and memory the container is using.
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