wsl2-vmmem-fix
Helpful changes to fix vmmem eating up available physical memory and flooding your disk.
Systems with low amounts of physical RAM can benefit the most of these changes.
One reason why vmmem process uses so much memory..
ANSWER: IT IS THE FILE CACHING! :(
The high VM memory usage (in windows process vmmem) is because
linux caches files for better performance.
Most notable memory increase is because Docker images are also files (!) and are included into this cache!
To confirm this, try running some Docker containers and compare the memory usage before/after.
# linux
free -mh (see "buff/cached" memory)
# windows
vmmem (see process memory usage)
The buff/cached memory is increased by the size of the docker image file being used!
Linux
Disable swappiness
"The swappiness in Linux is a rate in which the operating system tends to write data out of the RAM onto the disk drive (HDD or SSD)"
Letting VM to compensate lack of memory (RAM) by allowing it to flush to disk
will slow the host system down ALOT and burn trough your ssd/nvme disk also faster!
To avoid these problems disable swapiness in /etc/sysctl.conf:
vm.swappiness=0
Apply changes with sudo sysctl -p command.
NB! Increase your memory limit in
.wslconfigif it is not enough for VM!
Forcing distro to release cached files memory
WSL distro kernel tries to re-claim small amounts of memory
back to host by running periodically (when CPU is idle):
echo 1 > /proc/sys/vm/compact_memory
This can be seen in dmesg -T logs:
villisco@blackbox:~$ dmesg -T
...
[Sun Oct 9 13:04:51 2022] WSL2: Performing memory compaction.
[Sun Oct 9 13:05:52 2022] WSL2: Performing memory compaction.
[Sun Oct 9 13:06:57 2022] WSL2: Performing memory compaction.
But this will not re-claim most of the files cached in memory space.
To force kernel to clear caches use:
echo 1 > /proc/sys/vm/drop_caches
NB! This will free the memory but could slow down
the performance/speed when working with WSL distro.
Read more about the WSL memory reclaiming:
https://devblogs.microsoft.com/commandline/memory-reclaim-in-the-windows-subsystem-for-linux-2/
Windows
WSL limits
WSL resource usages can be limited by .wslconfig file.
Place this file in Windows:
C:/Users/{username}/.wslconfig
Read more about available .wslconfig settings:
https://learn.microsoft.com/en-us/windows/wsl/wsl-config