Skymont: Intel's E-Cores reach for the Sky (2024)

I still don’t quite get how the cpu knows what is low priority or background. Or is that steered at OS level a bit like cpu pinning ?

When the P/E model was introduced by Intel, there was a fairly long transition period where both Windows and Linux performed unpredictably poorly for most compute-intensive work loads, to the point where the advice was to disable the E cores entirely if you were gaming or doing anything remotely CPU-intensive or if your OS was never going to be updated (Win 7/8, many LTS Linux).

It's not entirely clear to me why it took a while to add support on Linux because the kernel already supported big.LITTLE and from the scheduler's point of view it's the same thing as Intel's P/E cores. I guess the patch must've been simple but it just took very long to trickle down to common distributions?

Not very surprisingly but IME running VMs you still want to pin (at least on Linux).

Right so how does the scheduler know what’s low priority?

I thought this was actually a good question, so I have trued to look it up. If I understand correctly the CPU tells the scheduler! I could not find exactly how though, maybe an MSR?