Ampere Preparing The ARM64 Linux Kernel To Support Higher CPU Core Counts

[phoronix]

Phoronix: Ampere Preparing The ARM64 Linux Kernel To Support Higher CPU Core Counts

Ampere Computing has sent out its latest patch attempt at increasing the number of Arm CPU cores supported by the mainline Linux kernel. As it stands at the moment the 64-bit ARM mainline Linux kernel build supports 256 cores, which can be exceeded with Ampere's new AmpereOne processors in a multi-socket configuration...

https://www.phoronix.com/news/Ampere-More-ARM-Cores-Linux

[stormcrow]

... especially short sighted of the Linux kernel people as the typically slower moving and more conservative FreeBSD already has this support in v 14. One of the reasons 14 is a boost in performance over 13 is they reworked some of the way they manage cores and high core count systems.

[some_canuck]

Keeping a low limit is being done simply to save memory: each supported CPU core adds around 8KB to the kernel image size.

My arm kernels are around 35mb (on disk, let alone at runtime)... a whopping 8k means nothing to me.

[ehansin]

My arm kernels are around 35mb (on disk, let alone at runtime)... a whopping 8k means nothing to me.

My reading of the following...

With the proposed patches, when CPUMASK_OFFSTACK is enabled, the limit is to be raised to 8,192 or otherwise 512 CPU cores. Keeping a low limit is being done simply to save memory: each supported CPU core adds around 8KB to the kernel image size.

...is that each supported CPU core creates and additional 8K in the kernel image, so if you enabled support for the full 8,192 cores, you get and ( (8192 * 8) / 1024) ) ~64MB increase in kernel size. And if my math is right, would be ~4MB for 512 cores; not as bad of course. Sounds like enabling the CPUMASK_OFFSTACK makes assignment (more?) dynamic. I guess what I am getting at is that enabling the full 8,192 by default without any dynamic adjustments would increase the kernel image by quite a bit, assuming I'm following things correctly.

[Volta]

... especially short sighted of the Linux kernel people as the typically slower moving and more conservative FreeBSD already has this support in v 14. One of the reasons 14 is a boost in performance over 13 is they reworked some of the way they manage cores and high core count systems.

It seems you have no clue, but it didn't stop you from posting a comment. P.S. slower moving and more conservative is now synonyme to lack of resources?