Re: [PATCH 4/4] riscv: enable HAVE_FAST_GUP if MMU

[Jisheng Zhang <jszhang@kernel.org>]

On Sun, Dec 31, 2023 at 07:37:33AM +0100, Alexandre Ghiti wrote:
> On 19/12/2023 18:50, Jisheng Zhang wrote:
> > Activate the fast gup for riscv mmu platforms. Here are some
> > GUP_FAST_BENCHMARK performance numbers:
> > 
> > Before the patch:
> > GUP_FAST_BENCHMARK: Time: get:53203 put:5085 us
> > 
> > After the patch:
> > GUP_FAST_BENCHMARK: Time: get:17711 put:5060 us
> 
> 
> On which platform did you run this benchmark?

T-HEAD th1520(cpufreq isn't enabled since the clk/pll isn't upstreamed,
so cpu is running at the default freq set by u-boot)
> 
> 
> > 
> > The get time is reduced by 66.7%! IOW, 3x get speed!
> 
> 
> Well done!
> 
> Thanks,
> 
> Alex
> 
> 
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> >   arch/riscv/Kconfig               | 1 +
> >   arch/riscv/include/asm/pgtable.h | 6 ++++++
> >   2 files changed, 7 insertions(+)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index d3555173d9f4..04df9920282d 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -119,6 +119,7 @@ config RISCV
> >   	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
> >   	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
> >   	select HAVE_EBPF_JIT if MMU
> > +	select HAVE_FAST_GUP if MMU
> >   	select HAVE_FUNCTION_ARG_ACCESS_API
> >   	select HAVE_FUNCTION_ERROR_INJECTION
> >   	select HAVE_GCC_PLUGINS
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index ab00235b018f..c6eb214139e6 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -673,6 +673,12 @@ static inline int pmd_write(pmd_t pmd)
> >   	return pte_write(pmd_pte(pmd));
> >   }
> > +#define pud_write pud_write
> > +static inline int pud_write(pud_t pud)
> > +{
> > +	return pte_write(pud_pte(pud));
> > +}
> > +
> >   static inline int pmd_dirty(pmd_t pmd)
> >   {
> >   	return pte_dirty(pmd_pte(pmd));