Re: [External] Re: [PATCH] RISC-V: add uniprocessor flush_tlb_range() support

[Jisheng Zhang]

On Mon, Jan 29, 2024 at 04:26:57PM +0800, yunhui cui wrote:
> Hi Jisheng,
> 
> On Mon, Jan 29, 2024 at 4:02 PM Jisheng Zhang <jszhang@xxxxxxxxxx> wrote:
> >
> > On Thu, Jan 25, 2024 at 02:20:44PM +0800, Yunhui Cui wrote:
> > > Add support for flush_tlb_range() to improve TLB performance for
> > > UP systems. In order to avoid the mutual inclusion of tlbflush.h
> > > and hugetlb.h, the UP part is also implemented in tlbflush.c.
> >
> > Hi Yunhui,
> >
> > IIRC, Samuel sent similar patch series a few weeks ago.
> >
> > https://lore.kernel.org/linux-riscv/20240102220134.3229156-1-samuel.holland@xxxxxxxxxx/
> >
> > After that series, do you still need this patch?
> 
> Thank you for your reminder. I didn't find it before I mailed my
> patch. I just looked at the content of this patch. I understand that
> my patch is needed. For a single core, a more concise TLB flush logic
> is needed, and it is helpful to improve performance.

Currently, riscv UP flush_tlb_range still use flush all TLB entries,
obviously it's is a big hammer, this is what your patch is trying to
optimize. I'm not sure whether I understand your code correctly or not.
Let me know if I misunderstand your code.

After patch5 of the Samuel's series, __flush_tlb_range is unified for
SMP and UP, so that UP can also benefit from recent improvements, such
as range flush rather than all.

Thanks

> 
> Thanks,
> Yunhui