Pedro.

Thanks for the comments.

I agree that detailed commit message helps to explain that this MADT order change is to help some
legacy APPs that assume the high performance cores are before low performance ones in MADT
and use OS APIs to explicitly request running on certain target cpu cores to get higher APP performance.

Thanks,

Ray

From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Pedro Falcato
Sent: Saturday, November 19, 2022 3:11 AM
To: Lin, JackX <jackx.lin@intel.com>
Cc: devel@edk2.groups.io; Chiu, Chasel <chasel.chiu@intel.com>; Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>; Oram, Isaac W <isaac.w.oram@intel.com>; Gao, Liming <gaoliming@byosoft.com.cn>; Dong, Eric <eric.dong@intel.com>; Kuo, Donald <donald.kuo@intel.com>; Kumar, Chandana C <chandana.c.kumar@intel.com>
Subject: Re: [edk2-devel] [edk2-platforms: PATCH] BIOS needs to present cores in order of relative performance in MADT

On Fri, Nov 18, 2022 at 8:35 AM Lin, JackX <jackx.lin@intel.com> wrote:

Hi Pedro,

Yes, it is for  some specific test tools.

There are different performance between CPU cores, and the big cores are better than small cores.

Some legacy tools are executing with the highest performance CPU cores, In early CPU design, it is usually the first one.

We have to put them at the front of all CPU cores, otherwise some tests cannot pass.

Due to avoid this happened, we need to ensure CPU cores are ordered by big core first.

Thank you for the thorough description. Could you please (or whoever is pushing this) add this to the commit message?

I've been following the evolution of this specific file over the last few months with mild interest and getting things properly documented should be pretty important!

Might help avoid any future breakage too :D

Thanks,

Pedro