Take Control of Your WSL Resources for Smooth Development

When WSL (Windows Subsystem for Linux) was first introduced to the scene I was so excited to use it, because it marked a big leap forward in building out the Windows Developer Experience, and as the second revision of it hit the PCs, it introduced big performance improvements and it made sense to switch some of my development to Windows.

The Problem

In the age of cloud computing, containers, orchestration, resources someone's PC has can brake the development experience and with WSL the resources by default are unlimited, that means that WSL can take all of your CPU & RAM with Windows.

While running Docker Desktop and two containers that are literally don't do anything, one of them is a postgres instance and the other a simple fastapi that returns Hello World I get over 5 GB of RAM usage, scale that up to something that has business logic and more containers, and you won't be able to open Chrome.

The Solution

The solution to this problem is to create a .wslconfig file where we will define the amount of resources WSL can use.

The solution will consist of configuring the RAM usage, the maximum capacity it can use, the CPU cores and the SWAP memory over all of theses we will go in detail and why you would or wouldn't allow WSL to take up these resources.

Configuring Resources

To configure resources we need to locate the .wslconfig file which will be located inside of the %USERPROFILE%. The easiest way to locate that folder is to open Run and type in %USERPROFILE%.

Once there, check if the file .wslconfig exists; if it doesn't - create it and it should look like the one in the picture below:

The caveat here with configuring the resources is that you need to keep in mind that you are running two systems in parallel, and that each one of them has to have resources, and that both of them will have their spikes in load - depending of the usage.

For example: I use WSL for development, where I need to use Docker which is heavy on RAM and CPU; and Windows for web browsing, entertainment, writing articles and playing video games.

This configuration applies to WSL2, so make sure you have that version, because it is more powerful then WSL1.

Now if the file was not created, add the following line on top of the file:

    [wsl2]
                                  

CPU Resources

To configure how much CPU cores WSL will use, you can add the variable:

    processors=6
                                  

This tells WSL that it has 6 cores allocated to work with. Based on your CPU and Workloads you can allocate more or less. Keep in mind that WSL won't go over the defined limit here, so once it peeks at a certain point you can adjust the resources again.

RAM Resources

To configure how much RAM you allocate to WSL you add the following line:

    memory=8GB
                                  

This will tell WSL not to go over 8 GB of RAM. While configuring RAM, you need to keep in mind that RAM can be utilized fairly quickly, and this connects us to the next variable: that we will define Swap.

Swap Resources

Swap comes in place when the whole RAM is utilized, then the system uses the secondary memory to keep the data of running applications instead of RAM, because it is full.

Depending on the load that you will carry out, you can allocate more or less, but I usually know that my current Kubernetes cluster will peek at 22 GB of RAM usage, and with that, I like to configure my swap 2 x 8, which means I will have 8 GB of RAM x 2, my swap will be 16 GB, which leaves room for the application to use more, but not to slow down.

    swap=16GB
                                  

I came across situations where I didn't want WSL to use Swap memory:

• I was training a Machine Learning model, and it wasn't as fast as real RAM, and you want to keep that in mind if you want to do this.
• It can wear your SSD down, because SSD have a specific amount of Read & Write Cycles, and once overridden - they fail. What is SSD write cycle? | Definition from TechTarget
• When you have a HDD, please don't do this and buy a SSD :)

After we did all of this work you file should look something like this:

    [wsl2]

    memory=8GB
                                        
    swap=16GB
                                        
    processors=4                                 
                                     

Save this, and go into your PowerShell session and shutdown WSL:

    wsl --shutdown
                                    

After this run WSL with your favourite distro, and the resources won't go over the limits that you have defined.

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