Linux Kernel 5.15 - Realtime preemption locking core merged

I guess this belongs in news?

though the kernel must be built with the REALTIME configuration option to use them)

Been worked on since 2004, it seems. I wonder if this is related to the things Wendell talk about in the video about the P5800X?

Or maybe it’s the opposite? I don’t know

4 Likes

This is awesome! I use a machine control software that uses rt_preempt (linuxcnc)… It will be nice not to have to install a different kernel to get the functionality…

This is pretty much to give Linux the option to do hard realtime scheduling.

Do note, hard realtime scheduling SUCKS from a gamer / regular user perspective, so not very useful on a Linux desktop (imagine getting stutters in your video feed while gaming, for instance). That said, PREEMPT_RT finally getting all patches in is great news for those of us insane enough to build products on it. :slight_smile:

With RT Linux, expect to be able to keep hard deadlines of around 2 ms at 60% single threaded load. Lower is possible but requires heavy fine-tuning, sacrifice of a goat and possibly removing core system daemons.

2 Likes

Hail the time gods

I dont really truly know what it means but I wonder if it will help further mitigate sidechain attacks like spectre and meltdown?

The “locking” and “core” are giving me that kind of vibe. Can anyone in the community dumb it down and do a quick ELI5 for us curious but security concious non-devs?

I think the official PREEMPT_RT website does a fantastic job of this already, but, in essence it is about predictable behavior on a Turing machine (yes, this is an oxymoron).

This is for small embedded devices, possibly with a screen or web server, that needs some realtime but also want to offer soft services where latency is not as important, such as a lightweight webserver spitting out SOAP info. Think smart washing machine or one of those fancy power splitters that integrate power between battery and solar for home use.

As for security, this will not help at all with sidechains, that is a whole different can of worms. Of course, these changes could fix bugs allowing these attacks, but that would be by accident, not design.

2 Likes