CODEWITHSUNDEEP
dockercontainers
user3398900
user3398900

Reputation: 845

How to check the number of cores used by docker container?

I have been working with Docker for a while now, I have installed docker and launched a container using 

docker run -it --cpuset-cpus=0 ubuntu

When I log into the docker console and run 

grep processor /proc/cpuinfo | wc -l

It shows 3 which are the number of cores I have on my host machine.

Any idea on how to restrict the resources to the container and how to verify the restrictions??

Upvotes: 9

Views: 42622

Answers (4)

Matt
Matt

Reputation: 74740

Containers aren't complete virtual machines. Some kernel resources will still appear as they do on the host.

In this case, --cpuset-cpus=0 modifies the resources the container cgroup has access to which is available in /sys/fs/cgroup/cpuset/cpuset.cpus. Not what the VM and container have in /proc/cpuinfo.

One way to verify is to run the stress-ng tool in a container:

Using 1 cpu will be pinned at 1 core (1 / 3 cores in use, 100% or 33% depending on what tool you use):

docker run --cpuset-cpus=0 deployable/stress -c 3

This will use 2 cores (2 / 3 cores, 200%/66%):

docker run --cpuset-cpus=0,2 deployable/stress -c 3

This will use 3 ( 3 / 3 cores, 300%/100%):

docker run deployable/stress -c 3

Memory limits are another area that don't appear in kernel stats

$ docker run -m 64M busybox free -m
             total       used       free     shared    buffers     cached
Mem:          3443       2500        943        173        261       1858
-/+ buffers/cache:        379       3063
Swap:         1023          0       1023

yamaneks answer includes the github issue.

Upvotes: 7

user3398900
user3398900

Reputation: 845

docker inspect <container_name>

will give the details of the container launched u have to check for "CpusetCpus" in there and then u will find the details.

Upvotes: 9

yamenk
yamenk

Reputation: 51778

The issue has been already raised in #20770. The file /sys/fs/cgroup/cpuset/cpuset.cpus reflects the correct output.

The cpuset-cpus is taking effect however is not being reflected in /proc/cpuinfo

Upvotes: 14

sanath meti
sanath meti

Reputation: 6537

it should be in double quotes --cpuset-cpus="", --cpuset-cpus="0" means it make use of cpu0.

Upvotes: -3

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