On Mon, 2020-07-20 at 10:55 +0200, Kevin Kofler wrote: > That said, I do not see how the EarlyOOM heuristic, which allows, depending > on the exact settings, something like 80-90% of swap to be used IN ADDITION > to 90+% RAM (and will only start doing anything if BOTH RAM and swap are > full) can prevent thrashing in any reliable way. My thrashing scenarios have > had much less swap than that used. (I have twice as much swap than RAM, so > when the EarlyOOM heuristics trigger, my programs are already trying to use > almost 3 times as much RAM as is actually available!) Yeah, I think that EarlyOOM will mostly help in the scenario where you end up not having enough file caches to run your processes. I do believe that this is a common scenario where the machine continues to thrash for long periods[1]. In most cases where plenty of swap is available, the symptoms should be a lot less sever. i.e. I would expect it to become really sluggish, but things *should* recover much more quickly. Though, e.g. a fork-bomb could easily cause something like that. Anyway, I think to resolve it, we really need to enable the CPU and IO cgroup controllers. CPU is easy (you just need to set a few properties in systemd), but there are some road blocks to get the IO controller working. Also, we can probably fix systemd-logind hanging simply by assigning a MemoryLow= allocation of e.g. 60M to system.slice and also setting either DisableControllers=memory (create a large pool of memory for all system services) or DefaultMemoryLow=X (delegate memory further to each service separately). Benjamin [1] To be honest, I am wondering if some process might have actually filled up all the RAM even in your case. It can be hard to tell later on what exactly happened.
Attachment:
signature.asc
Description: This is a digitally signed message part
_______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
