I am having a Docker image of virtual size 6.5 GB
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
Image_Name latest d8dcd701981e About an hour ago 6.565 GB
but the RAM in my system is only 4GB , the container is working at a good speed though , I am really confused as how the RAM allocation is done for the docker containers . Is there any limit to the RAM size being allocated to a container as in the end docker container is just another isolated process running in the Operating system.
The virtual size of an image has nothing to do with memory allocation
If your huge image, once launched as a container, does very little, it won't reserve much memory (not consume much CPU)
For more on memory allocation, see this answer: you can limit at runtime the maximum memory allocation. And that, independently of the image size.
For example:
$ docker run -ti -m 300M --memory-swap -1 ubuntu:14.04 /bin/bash
We set memory limit and disabled swap memory limit, this means the processes in the container can use 300M memory and as much swap memory as they need (if the host supports swap memory).
Related
Can anyone tell me why RAM is released when dangling and unused images are deleted?
I have a Swarm Cluster with 3 nodes to 8Gb RAM each and 100 Gb HDD Memory
Note that there is no free RAM left at all, docker stats does not show prohibitive memory values.
The solution was to use the docker images prune -f command
And as you can see by the graphics, not only has HDD memory been released, but RAM as well
So dangling and unused images back up RAM?
I can’t understand
I have assigned 2GB of RAM memory as maximum memory limit for the docker container while creating the same. Now that more memory is required, is there way to increase the maximum RAM limit for the existing container?
I used the following command to create the container.
docker run --name=mysql_50000 -m 2g -p 50000:3306 mysql_docker_image_v4
It worked fine as expected. My container has a maximum memory limit of 2GB. I need it to be 3GB now. Any help is appreciated. Thanks
Please use docker update command with appropriate parameters (-m 3G). See doc:
https://docs.docker.com/engine/reference/commandline/update/
I have a vm flexible to change CPU and Memory on it. I have 5 containers running on it.The 3 three slave containers execute test cases.But when I run the containers,I see that the entire CPU is being filled.Even I increase the size of CPU ,it is also being filled.How do I overcome it.
Limiting the size of each container is the only option??
You can limit a container's resources (memory and CPU) at run-time. For example :
docker run --cpus=".5" my-container
to allow only 50% of a CPU for my-container.
Those settings are run-time settings, so you cannot set them in your Dockerfile.
I'd like to constrain the memory of a Docker container to 1 GB. According to the documentation, we can specify the desired memory limit using the --memory option:
$ docker run --memory <size> ...
However, the documentation does not describe the format or units for the argument anywhere on the page:
--memory , -m Memory limit
What units should I supply to --memory and other related options like --memory-reservation and --memory-swap? Just bytes?
Classic case of RTFM on my part. The --memory option supports a unit suffix so we don't need to calculate the exact byte number:
-m, --memory=""
Memory limit (format: <number>[<unit>], where unit = b, k, m or g)
Allows you to constrain the memory available to a container. If the
host supports swap memory, then the -m memory setting can be larger
than physical RAM. If a limit of 0 is specified (not using -m), the
container's memory is not limited. The actual limit may be rounded up
to a multiple of the operating system's page size (the value would be
very large, that's millions of trillions).
So, to start a container with a 1 GB memory limit as described in the question, both of these commands will work:
$ docker run --memory 1g ...
$ docker run --memory 1073741824 ...
The --memory-reservation and --memory-swap options also support this convention.
Taken from the docker documentation:
Limit a container’s access to memory Docker can enforce hard memory
limits, which allow the container to use no more than a given amount
of user or system memory, or soft limits, which allow the container to
use as much memory as it needs unless certain conditions are met, such
as when the kernel detects low memory or contention on the host
machine. Some of these options have different effects when used alone
or when more than one option is set.
Most of these options take a positive integer, followed by a suffix of
b, k, m, g, to indicate bytes, kilobytes, megabytes, or gigabytes.
This page also includes some extra information about memory limits when running docker on Windows.
docker run -m 50m <imageId> <command...>
This is how it should be given. This forces the docker container to use 50m of memory. As soon as it tries to use more than that, it will be shut down.
However using free -m you won't be able to see anything related to the container memory usage. you have to go inside it to see allowed memory.
I need to have a Docker Container with 6gb of RAM memory.
I tried this command:
docker run -p 5311:5311 --memory=6g my-linux
But it doesn't work because I logged in to the Docker Container and I checked the amount of memory available. This is the output which shows there are only 2gb available:
>> cat /proc/meminfo
MemTotal: 2046768 kB
MemFree: 1747120 kB
MemAvailable: 1694424 kB
I tried setting the preferences -> advance in the Docker Application.
If I set 6gb, it works... I mean, I have a container with 6gb MemTotal.
In this way all my containers will have 6gb...
I was wondering how to allocate 6gb of memory for only one container using some commands or setting something in the Docker File. Any help?
Don't rely on /proc/meminfo for tracking memory usage from inside a docker container. /proc/meminfo is not containerized, which means that the file is displaying the meminfo of your host system.
Your /proc/meminfo indicates that your Host system has 2G of memory available. The only way you'll be able to make 6G available in your container without getting more physical memory is to create a swap partition.
Once you have a swap partition larger or equal to ~4G, your container will be able to use that memory (by default, docker imposes no limitation to running containers).
If you want to limit the amount of memory available to your container explicitly to 6G, you could do docker run -p 5311:5311 --memory=2g --memory-swap=6g my-linux, which means that out of a total memory limit of 6G (--memory-swap), upto 2G may be physical memory (--memory). More information about this here.
There is no way to set memory limits in the Dockerfile that I know of (and I think there shouldn't be: Dockerfiles are there for building containers, not running them), but docker-compose supports the above options through the mem_limit and memswap_limit keys.