Re: [v2 PATCH] RISC-V: Optimize tlb flush path.

hch
2019-08-20T09:22:16Z

On Tue, Aug 20, 2019 at 08:42:19AM +0000, Atish Patra wrote:
> cmask NULL is pretty common case and we would be unnecessarily
> executing bunch of instructions everytime while not saving much. Kernel
> still have to make an SBI call and OpenSBI is doing a local flush
> anyways.
>
> Looking at the code again, I think we can just use cpumask_weight and
> do local tlb flush only if local cpu is the only cpu present.
>
> Otherwise, it will just fall through and call sbi_remote_sfence_vma().

Maybe it is just time to split the different cases at a higher level.
The idea to multiple everything onto a single function always seemed
odd to me.

FYI, here is what I do for the IPI based tlbflush for the native S-mode
clint prototype, which seems much easier to understand: