I think the ~/.mozilla/firefox/XXX.default-YYY/storage/default/https+++ZZZ.com/cache/https+++domain.com/ style dirs are the storage for what's called "service workers" which is persistent code related to each website that sends notifiications even if no related tab is open.
Suppose you have a favorite website that sells something, you might register with them that you're interested in a particular kind of product. A serviceworker for that site would be in the "ZZZ" folder named after that site, the code in there would run even if you don't have a tab open for that site. It's done so you can get a notification. In other cases it's some other code that the web designers don't want to have to reload each time you visit, caching it in your storage folder saves time and network.
You can see all your service workers in the Firefox menu: Help -> More troubleshooting information -> about:serviceworkers ( or load about:serviceworkers )
v1.6.0 has been released with this feature; prefix your source image configuration with docker:// to use a base image stored in the Docker daemon.
Gradle: jib.from.image = 'docker://docker-image'
Maven: <from><image>docker://docker-image</image></from>
The purgeServerSideCache method is deprecated and calling it has no effect - you'll get a console warning about that. This method is now replaced with refreshServerSideStore
slabtop command (part of the package procps) shows top memory objects used by the kernel.
dstat can help you figure out what is happening. dstat -cdnpmgs --top-bio --top-cpu --top-mem
Also have a look at smem ("smem -kt"), it can show you nicely what is in your swap.
ZRAM if you have no HDD/SSD swap partition.
ZSWAP if you do have a HDD/SSD swap partition.
ZCACHE: It does what ZSWAP does and ALSO compresses and speeds the filesystem page cache. (It is internally much more complicated and is not in the mainline kernel as it is still under development).