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

Atish Patra
2019-08-20T20:28:45Z

On Tue, 2019-08-20 at 02:22 -0700, hch@infradead.org wrote:
> 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:
>
> http://git.infradead.org/users/hch/riscv.git/commitdiff/ea4067ae61e20fcfcf46a6f6bd1cc25710ce3afe

This does seem a lot cleaner to me. We can reuse some of the code for
this patch as well. Based on NATIVE_CLINT configuration, it will send
an IPI or SBI call.

I can rebase my patch on top of yours and I can send it together or you
can include in your series.

Let me know your preference.

--
Regards,
Atish