> So, when powered by AC power, schedule everything on P cores when possible, schedule processes that eat a lot of CPU on P cores, same for any process with a negative nice value.

Even when plugged in, you may have thermal limitations. P cores will chew through your power budget more aggressively than E cores. For latency-sensitive workloads you do want to emphasize the P cores, but when throughput is the goal you'll usually be better off not ignoring the E cores, and not trying to run the P cores at high frequency where they're much less efficient. Intel started adding E cores to consumer chips in large part so they could score better on throughput-oriented multithreaded benchmarks like Cinebench; they're decent at compiling code, too, but you'll still want the P core for the linker.

That's not really how nice levels have worked traditionally, and would disallow specifying "run on Performance cores, but yield to other processes quickly".

I think that here is where things are lacking. There's not enough information that can be conveyed to the OS with just a number, and the number seems fixed and not tied to user input (active application, user just clicked, action blocking presentation).

It'd be cool if tasks told you about their workload in terms of latency throughput, and cadence required (hello skipping audio when you compile hard).

>when powered by AC power, schedule everything on P cores when possible

Sometime I feel like that is undesirable. It may make system consume more power, thus more heat output and louder.

I may be completely wrong, but I read that E cores are not power efficient, rather they are die space efficient.

FWIW, Apple leaves it up to the app developer to specify a quality-of-service for a particular execution context:

https://developer.apple.com/library/archive/documentation/Pe...

The problem is you don't really think about those cases early enough to matter. 7 minutes of battery isn't even a knowable thing - that is current average (though often not calculated that well) and could be 10 minutes if nothing happens (no emails arrive, no web pages rendering in the background, don't touch anything on it....), but if you try to run that 5 minute task in reality you have 2 minutes of CPU using the P cores, or 5 minutes using the E cores - but on the E cores you need 7 minutes. The above times are all made up of course, but they give the idea.

If when the battery is full you make the right decisions your battery can last longer. However this isn't something you can do. You don't want a pop-up when your email program spawns a thread to check for new email - programs do this all the time and the system doesn't know if the thread itself will run for a few ms or for hours. In most cases the battery consumed by the popup will be more than the thread itself uses. You want the system to make the right decisions - but the right decision depends on your system and someone else with a difference CPU may need different decisions.

I feel like cases 1, 2, and 3 broadly fit into "Battery Saver", "Performance", and "Battery Saver" modes?