Does it actually work?

Posted Apr 14, 2025 10:39 UTC (Mon) by khim (subscriber, #9252)
In reply to: Does it actually work? by taladar
Parent article: Three ways to rework the swap subsystem

Login? What login? It wasn't uncommon for me to not be able to login on a text console because after I type my username and hit enter I never get to the Password prompt because getty kill that session for “inactivity” before that may happen.

I have no idea how much work /bin/login does, but couldn't imagine why that would take 5 minutes or more on any system where swap works properly.

This stopped, of course, after I gave up and switched to the use of Linux in container. With browser outside of it.

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Does it actually work?

Posted Apr 14, 2025 22:14 UTC (Mon) by mbunkus (subscriber, #87248) [Link] (3 responses)

I can confirm khim's description. It's spot on & not hyperbole in the least. I've found myself in the exact same situation several times over the last several years. When this happens, no login method works at all (local console, ssh, display manager if it happens to be running on that server) due to how incredibly long each. and. every. key. stroke. takes. Debugging in such a situation is completely impossible, let alone fixing anything. Even if I manage to log in getting a process list takes multiple tens of minutes. The only sane thing to do is to hard reboot & eat the file system damage & loss of data.

And that sucks so much.

BTW, all of those cases were severs, not desktop systems.

Does it actually work?

Posted Apr 18, 2025 23:32 UTC (Fri) by Jandar (subscriber, #85683) [Link] (2 responses)

> The only sane thing to do is to hard reboot & eat the file system damage & loss of data.

I use ALT+SysReq+{s,u,s,b} in that order with a few seconds between. That's my way out of the semi-regular freezes apparently caused by swapping. Every time I have to do this I cross my fingers and pray to the filesystem-gods to spare my home directory ;-)

Does it actually work?

Posted Apr 24, 2025 16:00 UTC (Thu) by paulj (subscriber, #341) [Link] (1 responses)

SysRq is disabled by default now on some common distros. The point where you remember this is the point where you need it, but can no longer login to change this, of course.

Does it actually work?

Posted Apr 24, 2025 16:45 UTC (Thu) by farnz (subscriber, #17727) [Link]

Note, too, that SysRq's functions can be individually configured. On Fedora, the default setting is to allow sync, but nothing else; this is safe, since it's a function that the kernel will eventually do in the background, but not very powerful.

Does it actually work?

Posted Apr 24, 2025 16:08 UTC (Thu) by paulj (subscriber, #341) [Link]

Speaking of containers and browsers.... I used to run a system with a slow disk - plenty of RAM, but disk was slow enough that it was easy to trigger Linux's suicidal, "off a cliff edge", swap behaviour if I ignored the initial signs of slow-down from the bloated browser. I took to running the browser using 'systemd-run --user --slice -p MemoryMax=xG <browser>'. So it runs in a cgroup that will limit its memory use, and systemd-status --user can show you exactly how much RAM the entire group of browser processes is using, and it's also to kill the entire group - without needing to first run ps to find the process.