Simon Tatham12h ago

Another week, another tiny utility.

I was in a Zoom call last week with very poor video quality, which we figured out was because I was also running a long compile which wasn't leaving Zoom enough CPU to work with. So I paused the compile with ^Z and things improved.

Three hours after the call, I found the compile job, still suspended, in a window hidden behind something else. Oops. If only I'd been able to arrange to _automatically_ resume the job when the Zoom call terminated, instead of relying on my own memory!

I already have a tool 'after' which waits for a specified Unix process to terminate. But Zoom stays running even when not on a call, and there's no reason to suppose it puts the call in an easy-to-identify subprocess.

But it does put it in a separate _window_. So I wrote a tool 'xafter', which waits for a specified X window to close. Completely trivial – X11 makes it easy to ask for StructureNotify events on a window whether it's your own or not. Now if I suspend a job that's interfering with my meeting, I can immediately type 'xafter;fg' and select the meeting window, and then it'll restart automatically.

I have no idea if it would be easy to write analogues of this for Wayland, or Windows, or Mac.

Show threadwebhat
@simontatham nice, I need this
9:31amWeb
Show threadSimon Tatham12h ago
@webhat well reminded, I've now put a link in a followup post!
Show threadwebhat7h ago
@simontatham thank you 💜
Show threadMarcos Dione11h ago
@webhat @simontatham talking about nice, `nice -n 19 COMMAND` runs your command in the lowest CPU priority, which could have helped in this situation.
Show threadsmolwaffle9h ago
@mdione
Sometimes! But there are three problems:
1. nice does not affect I/O
2. Programs running in containers require cgroups settings instead
3. Thermally limited devices such as laptops will still throttle the CPU speed even if the priority of the processes creating the heat is low
@webhat @simontatham
Show threadwebhat7h ago
@smolwaffle @mdione @simontatham the processes would still be scheduled, it would just be interrupted more often. Many builds have multiple threads/jobs which are spawned, and with a lot of processes the CPU/scheduler might still throttle the Zoom call
Show threadMarcos Dione7h ago
@webhat @smolwaffle @simontatham I used tom compile software with `nice -n 19 make -j NUM_CPUS`, but that was a _long_ time ago. now I do an equivalent thing for map tiles, and it never seemed to interfere with the rest. Not sure I tried while zooming. Granted, part of it is IO bound (waiting for postgis to return data), but once it's deep enough (low data count per tile) it's all CPU bound. No complaints, on a 2018 laptop (32G, nvme disk).