Re: Status of Alder Lake support

Hi Kevin,

On 19.08.2022 20:50, Kevin Oberman wrote:
> What is the current state of support for Alder Lake CPUs with a mix of 
> "performance" and "Efficiency"  cores. I just received my first system 
> with such a processor and will be installing FreeBSD as soon as my SSD 
> arrives. I have no idea what issues I might run into. (Will it even work?)

Generally they work.  I have one in my lab since they appeared, and its 
biggest problem is UEFI console screwed by ASUS, which I partially 
fixed.  At some BIOS versions they also broke PXE booting, but then 
fixed it in later update.

The FreeBSD scheduler still has no idea about P and E cores, just trying 
to balance load equally based on cache topology (which is not symmetric 
there), but it is not too bad, since cores performance is not so 
dramatically different.

hwpmc(4) also does not differentiate P and E cores, and since they have 
different counters, it means that only few universal architectural 
counters are usable, which are sufficient for basic profiling though.

There were some stability issues reported, but were solved by either 
FreeBSD or BIOS update, so still not really diagnosed AFAIK.

-- 
Alexander Motin