slowfs simulates a slow filesystem for testing purposes. It uses builtin linux capabilities to do so, namely dm-delay. This is just a convenience wrapper around the technique shown in https://serverfault.com/a/954175.
To use, first create an image file to be mounted as a block device. For instance, this will create a 100MiB ext4 filesystem:
sudo ./create_image slow.img 200 mkfs.ext4Then mount it like so:
sudo mkdir -p /mnt/slow
sudo ./slowfs slow.img /mnt/slowThe image will remain mounted until you quit slowfs by typing q. Initially,
the filesystem does not add delay (e.g. so you can prepare the test environment
quickly). While running, slowfs will prompt for new delay values, and will
immediately change the delay to the new value.