Thanks for proper advice. I think LXDE wouldn't help much, since most memory is likely used by the apps instead of the system. Curiously, I enabled memory compression which was off by default and which helped me a lot with low-memory machines in the past — it's set to use 40% of the memory currently, but I might need to raise that. Unfortunately, I don't think it makes too much difference in the end.

I'll probably fiddle with the journaling parameters and rsyslog's options first, since those seem fairly harmless. Don't want to lose useful functionality right away.

I'm gonna move the system partition to an SSD sooner or later just to save what remains of my sanity, except the swap won't be there to avoid the device being hammered to death in a month or two before I can splurge on some mem upgrades. It's remarkable how twenty years ago I could glide through the filesystem as fast as my fingers diddled the cursor keys; or switch through images at 60 fps or so like a Terminator — but now I somehow have to constantly wait for the apps even with an SSD. Not quite sure what happened, but shit's wack.

firefox does a lot of disk caching during regular use, mostly from webapps trying to be clever about using your disk space to cache chats, media, etc. there’s functionally nothing you can do about this per-site. It also does a lot of journaling in local sqlite databases for its own cookies, history, caching, etc.

Ironically, I'm a webdev, so I'm somewhat sure that the sites I use don't behave that badly — and I just can't move so fast as to cause much i/o with the history and whatnot, exactly because it's barely responding when shit hits the fan. But I need to trace FF one of these days to figure out what the hell it's doing. Maybe the extensions are the culprits.