3 ms·

Why aren't modern systems just statically divided up, with known throughput-oriented junk homed on "efficiency cores" and known latency-sensitive tasks isolated

Why aren't modern systems just statically divided up, with known throughput-oriented junk homed on "efficiency cores" and known latency-sensitive tasks isolated on "performance cores", where each class of CPUs can use an optimal thread scheduler for its tasks? I know thread scheduling isn't the only thing users of lowlatency want, but I bet it solves the bulk of interactivity issues for desktop users.

wharvle 3y ago
How’d the BeOS scheduler work? Every desktop OS should just copy that. It felt like magic. Only thing I’ve seen since that even comes close is iOS, and it cheats by killing programs left and right (and has lost a little ground on that front over the years, anyway). QNX Photon wasn’t far off but was never a realistic option for an everyday desktop (even less so than BeOS, which was at least intended as such). Yeah, just copy BeOS.
- eitland 3y ago
  Where would you recommend that someone goes to look to learn how the BeOS scheduler works?
  - viraptor 3y ago
    https://www.haiku-os.org/ https://www.haiku-os.org/
    - eitland 3y ago
      That far I was able to get by myself ;-) I was wondering if someone had a good link to a book or paper or blog or something.
charcircuit 3y ago
Why not just give the latency sensitive processes a higher priority than those that aren't? If there are extra cycles on the latency sensitive cores you wouldn't want them to be idling. Trying to outsmart the scheduler can lead to worse scheduling so you have to measure the real world performance.
- jeffbee 3y ago
  You can't just wave your hands about having a scheduler that magically optimizes throughput and also promptly switches to a low-latency task as soon as it becomes runnable. There isn't one, because the way of sending the low-latency task to the CPU right away costs the throughput task some of its time.
lathiat 3y ago
macOS on Apple Silicon does exactly that: https://eclecticlight.co/2022/10/13/making-the-most-of-apple-silicon-power-3-controls/ https://eclecticlight.co/2022/10/13/making-the-most-of-apple... https://eclecticlight.co/2022/01/07/how-macos-controls-performance-qos-on-intel-and-m1-processors/ https://eclecticlight.co/2022/01/07/how-macos-controls-perfo...
viraptor 3y ago
You actually want the opposite for power saving. (Sometimes) Pipewire got a change recently from Asahi Linux to ensure that relatively rare audio interrupts don't wake up the performance cores and are left on efficiency ones.

wharvle 3y ago

How’d the BeOS scheduler work? Every desktop OS should just copy that. It felt like magic. Only thing I’ve seen since that even comes close is iOS, and it cheats by killing programs left and right (and has lost a little ground on that front over the years, anyway). QNX Photon wasn’t far off but was never a realistic option for an everyday desktop (even less so than BeOS, which was at least intended as such). Yeah, just copy BeOS.

eitland 3y ago
Where would you recommend that someone goes to look to learn how the BeOS scheduler works?
- viraptor 3y ago
  https://www.haiku-os.org/ https://www.haiku-os.org/
  - eitland 3y ago
    That far I was able to get by myself ;-) I was wondering if someone had a good link to a book or paper or blog or something.

charcircuit 3y ago

Why not just give the latency sensitive processes a higher priority than those that aren't? If there are extra cycles on the latency sensitive cores you wouldn't want them to be idling. Trying to outsmart the scheduler can lead to worse scheduling so you have to measure the real world performance.

jeffbee 3y ago
You can't just wave your hands about having a scheduler that magically optimizes throughput and also promptly switches to a low-latency task as soon as it becomes runnable. There isn't one, because the way of sending the low-latency task to the CPU right away costs the throughput task some of its time.

lathiat 3y ago

macOS on Apple Silicon does exactly that: https://eclecticlight.co/2022/10/13/making-the-most-of-apple-silicon-power-3-controls/ https://eclecticlight.co/2022/10/13/making-the-most-of-apple... https://eclecticlight.co/2022/01/07/how-macos-controls-performance-qos-on-intel-and-m1-processors/ https://eclecticlight.co/2022/01/07/how-macos-controls-perfo...

viraptor 3y ago

You actually want the opposite for power saving. (Sometimes) Pipewire got a change recently from Asahi Linux to ensure that relatively rare audio interrupts don't wake up the performance cores and are left on efficiency ones.