linux-kernel - Re: [PATCH v2 5/5] mm: Add update_mmu_tlb

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Date: Tue, 7 May 2024 00:07:14 +0800
From: Lance Yang <ioworker0@...il.com>
To: Bang Li <libang.li@...group.com>
Cc: akpm@...ux-foundation.org, chenhuacai@...nel.org, 
	tsbogend@...ha.franken.de, paul.walmsley@...ive.com, palmer@...belt.com, 
	chris@...kel.net, jcmvbkbc@...il.com, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, loongarch@...ts.linux.dev, 
	linux-riscv@...ts.infradead.org, david@...hat.com, ryan.roberts@....com, 
	libang.linux@...il.com
Subject: Re: [PATCH v2 5/5] mm: Add update_mmu_tlb_range()

On Mon, May 6, 2024 at 11:52 PM Bang Li <libang.li@...group.com> wrote:
>
> After the commit 19eaf44954df ("mm: thp: support allocation of anonymous
> multi-size THP"), it may need to batch update tlb of an address range
> through the update_mmu_tlb function. We can simplify this operation by
> adding the update_mmu_tlb_range function, which may also reduce the
> execution of some unnecessary code in some architectures.
>
> Signed-off-by: Bang Li <libang.li@...group.com>
> ---
>  include/linux/pgtable.h | 8 ++++++++
>  mm/memory.c             | 4 +---
>  2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 18019f037bae..869bfe6054f1 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -737,6 +737,14 @@ static inline void update_mmu_tlb(struct vm_area_struct *vma,
>  #define __HAVE_ARCH_UPDATE_MMU_TLB
>  #endif
>
> +#ifndef __HAVE_ARCH_UPDATE_MMU_TLB_RANGE

IIRC, the contemporary practice is to define a macro with the same name
as the function if it is being overridden.

Thanks,
Lance

> +static inline void update_mmu_tlb_range(struct vm_area_struct *vma,
> +                               unsigned long address, pte_t *ptep, unsigned int nr)
> +{
> +}
> +#define __HAVE_ARCH_UPDATE_MMU_TLB_RANGE
> +#endif
> +
>  /*
>   * Some architectures may be able to avoid expensive synchronization
>   * primitives when modifications are made to PTE's which are already
> diff --git a/mm/memory.c b/mm/memory.c
> index eea6e4984eae..2d53e29cf76e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4421,7 +4421,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>         vm_fault_t ret = 0;
>         int nr_pages = 1;
>         pte_t entry;
> -       int i;
>
>         /* File mapping without ->vm_ops ? */
>         if (vma->vm_flags & VM_SHARED)
> @@ -4491,8 +4490,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>                 update_mmu_tlb(vma, addr, vmf->pte);
>                 goto release;
>         } else if (nr_pages > 1 && !pte_range_none(vmf->pte, nr_pages)) {
> -               for (i = 0; i < nr_pages; i++)
> -                       update_mmu_tlb(vma, addr + PAGE_SIZE * i, vmf->pte + i);
> +               update_mmu_tlb_range(vma, addr, vmf->pte, nr_pages);
>                 goto release;
>         }
>
> --
> 2.19.1.6.gb485710b
>