/g/ - syscall of the day: sched_(get|set)affinity - Technology

Anonymous

syscall of the day: sched_(get(...) 05/04/26(Mon)08:57:52 No.108751329

File: 1708185469009524.jpg (100 KB, 500x500)

syscall of the day: sched_(get|set)affinity Anonymous 05/04/26(Mon)08:57:52 No.108751329 Archived

previous: >>108744281
#define __NR_sched_setaffinity        203
#define __NR_sched_getaffinity        204
https://man7.org/linux/man-pages/man2/sched_setaffinity.2.html

tl;dr:
manage your thread's allowed CPU(s)

pretty neat, and not overly complicated. see also https://man7.org/linux/man-pages/man7/cpuset.7.html
another API which is pretty annoying where you have to allocate, query, reallocate, etc. until you don't get EINVAL. take special care to ensure you don't overflow when they round up!
it's got a nice example program. i always really appreciate manpages that do that
anyway, yeah. good syscall. actually has quite a lot of real world uses, and though the API is kind of gross, it could certainly be worse. overall, i'm quite happy with it i'd say

relevant resources:
man man
man syscalls
https://man7.org/linux/man-pages/
https://linux.die.net/man/
https://elixir.bootlin.com/linux/
https://elixir.bootlin.com/musl/
https://elixir.bootlin.com/glibc/

Anonymous
05/04/26(Mon)09:22:46 No.108751448

Anonymous 05/04/26(Mon)09:22:46 No.108751448

>>108751329
syscalls r gay

Anonymous
05/04/26(Mon)09:45:49 No.108751576

Anonymous 05/04/26(Mon)09:45:49 No.108751576

>>108751329
syscall more like gaycall

Anonymous
05/04/26(Mon)13:28:44 No.108753129

Anonymous 05/04/26(Mon)13:28:44 No.108753129

>>108751576
what did she mean by this

Anonymous
05/04/26(Mon)13:32:08 No.108753153

Anonymous 05/04/26(Mon)13:32:08 No.108753153

>>108751329
syscall more like siscall

Anonymous
05/04/26(Mon)13:47:52 No.108753259

Anonymous 05/04/26(Mon)13:47:52 No.108753259

god I hope I'll never have NUMA cores

Anonymous
05/04/26(Mon)18:37:34 No.108754931

Anonymous 05/04/26(Mon)18:37:34 No.108754931

bump for the syscall sis.

Anonymous
05/04/26(Mon)19:31:39 No.108755188

Anonymous 05/04/26(Mon)19:31:39 No.108755188

File: 03BgPycPAdvgfPvvP04EDD0piUo=.gif (1.46 MB, 480x360)

1.46 MB GIF

so what I make this syscall and the system is going to accommodate the max number of threads to be used for a program in specific? Or controls the max number of threads for the while system unit

Anonymous
05/04/26(Mon)20:47:31 No.108755544

Anonymous 05/04/26(Mon)20:47:31 No.108755544

>>108755188
say you have CPUs numbed 0-3
with this syscall, you can restrict your process to any subset of those CPUs
so you could, in theory, have two different worker threads that you might want to pin to separate CPUs (say, 0 and 1, or even 0-1 and 2-3) so that they don't interfere with each other's cache

Anonymous
05/04/26(Mon)20:48:21 No.108755550

Anonymous 05/04/26(Mon)20:48:21 No.108755550

>>108751329
Syscall more like snailcat

Anonymous
05/05/26(Tue)00:02:02 No.108756314

Anonymous 05/05/26(Tue)00:02:02 No.108756314

>>108755544
thank you, you are very kind.

Anonymous
05/05/26(Tue)00:04:37 No.108756320

Anonymous 05/05/26(Tue)00:04:37 No.108756320

File: 1773539519661813.jpg (31 KB, 477x474)

31 KB JPG

>>108756314
i like helping anons to learn more about syscalls and the linux kernel! it makes me happy to see them interested in the discussion

Anonymous
05/05/26(Tue)02:19:55 No.108756791

Anonymous 05/05/26(Tue)02:19:55 No.108756791

>>108755544
>so that they don't interfere with each other's cache
What about systemd, and gnome, and the other bloat that keep running in the background on a Linux system?

Those will keep thrashing the cache. While two cpu bound threads will already span different cpu if the system is not under pressure, no need for these useless syscalls at all.

Anonymous
05/05/26(Tue)08:07:45 No.108757932

Anonymous 05/05/26(Tue)08:07:45 No.108757932

>>108756791
i don't use gnome, and systemd shouldn't be doing much
but there are plenty of circumstances where you might use this on non consumer hardware, or in other circumstances where you would expect to have more control over the processes running

Anonymous
05/05/26(Tue)09:51:28 No.108758379

Anonymous 05/05/26(Tue)09:51:28 No.108758379

>>108751329
I think this is メアリーさん.
Sex with メアリーさん.