X86_64 : 8 CPU limitation on Vanilla release

[Alberto Bursi]

On 09/07/21 10:03, Brice GIBOUDEAU via openwrt-devel wrote:
> 
> Hello,
> 
> I'm reaching out to you about a limitation on the X86_64 target.
> 
> We use this version to operate large scale Wireguard VPNs on VMs and physical servers (DELL & HP). The actual limitation of 8 CPU is the only reason why we have to recompile OpenWRT. This 8 CPU limitation makes perfect sense for most targets to save flash/memory  space but x86_64 have less physical limitations and most CPUs have more than 8 cores/threads.
> 
> Is it an option to raise this limitation to 64 to fit most available CPU on the market ?
> I'm not very use to patch submission but if it's needed I can try to do it.
> 
> What I can see the cost is an overhead 8KB memory and kernel size per extra CPU so (64-8)x8=448KB addition. X86_64 have less limitations than other architecture and enabling more CPUs should be ok for this platform.
> 


I think there is no problem to raise CPU core limit on x86_64 target to 
cover more than 8 cores, it was probably just an old default and nobody 
has asked to change it yet.

When you submit the patch properly see submission rules (1) you should 
also do the same change in the "config-5.10" file which is the kernel 
config for the next kernel version.


1. https://openwrt.org/submitting-patches

-Alberto