[Doc] Update description of vLLM support for CPUs

[DamonFool]

Hi all,

The description of CPU support in vLLM is out of date.
It would be better to update it.

Thanks.
Best regards,
Jie

[mgoin]

Since the AVX2 and PowerPC backends don't have active testing and this documentation assumes you are building on a machine with AVX512, I'm a little hesitant to update in this doc. Maybe if you call out specifically where you can get directions for AVX2 and PowerPC, and that this doc is assuming AVX512, that would be more clear.

[DamonFool]

Thanks @mgoin for the review.

The origin description AVX512 is required is quite misleading, which means vLLM requires AVX512 ISA to run.
It would limit the usage of vLLM if people wrongly get the msg that vLLM only supports AVX512.

Actually, we've built and run vLLM on AVX2-only machines.
So I would suggest removing AVX512 is required here.

However, if you're against adding the PowerPC CPUs here, I'm fine.
This is because we don't have PowerPC CPUs and don't test it at all.

Thanks.

[DamonFool]

Since the AVX2 and PowerPC backends don't have active testing and this documentation assumes you are building on a machine with AVX512, I'm a little hesitant to update in this doc. Maybe if you call out specifically where you can get directions for AVX2 and PowerPC, and that this doc is assuming AVX512, that would be more clear.

Hi @mgoin , I kept AVX512 in the doc.
But make it to be (optional, recommended) as the description of the compiler.
What do you think?
Thanks.