Hacker News Reader

Comment by lifty | Hacker News Reader

While I can't really know for sure, but based on perceived performance and smoothness, most likely M1 + MacOS already does something similar in terms of thread and process prioritisation. iOS has done this for a long time, making sure that rendering threads are not resource starved.

View on HN

AFAIK apple runs background tasks on slow cores which is supposed to free fast cores for foreground tasks.

I still don't understand why is it necessary in an OS which can juggle threads hundreds times per second using priority system. At least ignoring power efficiency aspect and concentrating only on performance or perceived performance aspects.

Context switching is a major performance killer on modern CPUs. You can look at the "slow" cores as being optimized for offloading context switches and interrupts across myriad threads so that the "fast" cores can focus on the primary workload with few context switches.

This is the same motivation behind why high-performance software architecture uses a "thread per core" model. There are large throughput gains to be had by minimizing context switching and CPU cache sharing across threads.

Do you know of any resources for learning CPU-bound parallel/concurrent programming? I wish it was easier to user all the cores my devices actually have. Asynchronous IO and network stuff is “easy” because you don’t care to much when then work completes as long as it’s not blocking the main thread, but speeding up CPU bound tasks is much harder. For all its flaws, Unity with their DOTS (and I believe specifically their job system) is the only thing that I am aware of that facilitates programmers multithreading CPU bound work (you can multithread actual gameplay code rather than just the standard rendering thread, game logic thread, IO thread, etc. of many games)rather than just having to roll your own solution.

HPC courses can be pretty good for that.

Stuff like OpenMP is great for doing quick things like a parallel for cycle

Reply on news.ycombinator.com