I was probably a bit imprecise; I do sometimes get full lock ups where I have to reboot, mostly when running TensorFlow locally, but usually I just get lock ups that last < 10 seconds when compiling things in the background.

It's at the level of "annoying, but doesn't impact my work", so I just live with it.

Ah I see. Which scheduler are using?

$ cat /sys/block/sda/queue/scheduler

noop deadline cfq [bfq]

I've been very pleased with the responsiveness of BFQ when multitasking.

And actually, I shouldn't say I never get lock-ups. There's been a couple times where the DE just freezes, and I'll have to hit Ctrl+Alt+F2 to switch to another tty and restart the display manager. But I attribute that to running bleeding-edge version of things and enabling experimental features, so that's fair.

Lastly, my MacBook Pro (2010 6,2) would also experience random freezes on Ubuntu (would have to power off/on) and upgrading the kernel from the Ubuntu default to latest mainline solved that problem completely.

$ cat /sys/block/sda/queue/scheduler cat: /sys/block/sda/queue/scheduler: No such file or directory

I guess my work does something weird with our desktop linux installs, laptop says this though:

$ cat /sys/block/sda/queue/scheduler noop [deadline] cfq

Last time I was running Ubuntu (a month or two ago), trying to use the wifi network management menu would easily lock up the interface for a while - I'm guessing it manages to do slow work on the main window manager thread. Maybe that's a common problem.

I've seen lengthy (10 seconds to an hour) freezes primarily when the system starts thrashing.

I've seen this too, I have two very similar specced workstations, one has consumer level SSD and the other has an older Intel S3500. Whenever I do heavy IO, the system with the consumer level SSD will start freezing.