Re: [RFT PATCH] riscv: mremap speedup - enable HAVE_MOVE_PUD and HAVE_MOVE_PMD

From: Palmer Dabbelt <palmer@dabbelt.com>
To: jszhang3@mail.ustc.edu.cn
Cc: Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFT PATCH] riscv: mremap speedup - enable HAVE_MOVE_PUD and HAVE_MOVE_PMD
Date: Sat, 22 May 2021 08:58:50 -0700 (PDT)	[thread overview]
Message-ID: <mhng-5de139d5-ac6e-4f73-9d63-721790b30c26@palmerdabbelt-glaptop> (raw)
In-Reply-To: <20210417003539.5bceabc2@xhacker>

On Fri, 16 Apr 2021 09:37:22 PDT (-0700), jszhang3@mail.ustc.edu.cn wrote:
> From: Jisheng Zhang <jszhang@kernel.org>
>
> HAVE_MOVE_PUD enables remapping pages at the PUD level if both the source
> and destination addresses are PUD-aligned.
> HAVE_MOVE_PMD does similar speedup on the PMD level.
>
> With HAVE_MOVE_PUD enabled, there is about a 143x improvement on qemu
> With HAVE_MOVE_PMD enabled, there is about a 5x improvement on qemu
>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> Hi all,
>
> After reading the risc-v privileged spec, I think it's safe to support
> the HAVE_MOVE_PUD and HAVE_MOVE_PMD optimization on riscv. The patch passed
> the mremap_test on QEMU. However this can't be tested on real HW due to lack
> of HW boards, this is the reason why I mark this patch as RFT. I hope I can
> buy a sipeed Allwiner D1 SoC powered SBC soon, at least I can test
> HAVE_MOVE_PMD. Helping me to test on real HW is appreciated!
>
> Thanks
>
>  arch/riscv/Kconfig               |  2 ++
>  arch/riscv/include/asm/pgtable.h | 12 ++++++++++++
>  2 files changed, 14 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index e8074d248457..37660de68b00 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -80,6 +80,8 @@ config RISCV
>  	select HAVE_KPROBES
>  	select HAVE_KPROBES_ON_FTRACE
>  	select HAVE_KRETPROBES
> +	select HAVE_MOVE_PMD
> +	select HAVE_MOVE_PUD
>  	select HAVE_PCI
>  	select HAVE_PERF_EVENTS
>  	select HAVE_PERF_REGS
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index ebf817c1bdf4..287733b95d10 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -360,6 +360,18 @@ static inline void set_pte_at(struct mm_struct *mm,
>  	set_pte(ptep, pteval);
>  }
>
> +static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
> +			      pmd_t *pmdp, pmd_t pmd)
> +{
> +	set_pmd(pmdp, pmd);
> +}
> +
> +static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
> +			      pud_t *pudp, pud_t pud)
> +{
> +	set_pud(pudp, pud);
> +}
> +
>  static inline void pte_clear(struct mm_struct *mm,
>  	unsigned long addr, pte_t *ptep)
>  {

Thanks, this is on for-next.

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