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Message-ID: <71cb77b8-c4b8-4d63-8b59-105440527c15@arm.com>
Date: Wed, 30 Apr 2025 15:16:08 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org
Cc: david@...hat.com, willy@...radead.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, catalin.marinas@....com, will@...nel.org,
Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, vbabka@...e.cz,
jannh@...gle.com, anshuman.khandual@....com, peterx@...hat.com,
joey.gouly@....com, ioworker0@...il.com, baohua@...nel.org,
kevin.brodsky@....com, quic_zhenhuah@...cinc.com,
christophe.leroy@...roup.eu, yangyicong@...ilicon.com,
linux-arm-kernel@...ts.infradead.org, namit@...are.com, hughd@...gle.com,
yang@...amperecomputing.com, ziy@...dia.com
Subject: Re: [PATCH v2 3/7] mm: Add batched versions of
ptep_modify_prot_start/commit
On 29/04/2025 06:23, Dev Jain wrote:
> Batch ptep_modify_prot_start/commit in preparation for optimizing mprotect.
> Architecture can override these helpers.
I would suggest merging this with patch #7 since that's where they actually get
used. Then you can add a single patch after that to specialize them for arm64,
which will give a performance win.
Thanks,
Ryan
>
> Signed-off-by: Dev Jain <dev.jain@....com>
> ---
> include/linux/pgtable.h | 38 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 38 insertions(+)
>
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index b50447ef1c92..ed287289335f 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -891,6 +891,44 @@ static inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
> }
> #endif
>
> +/* See the comment for ptep_modify_prot_start */
> +#ifndef modify_prot_start_ptes
> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> + unsigned long addr, pte_t *ptep, unsigned int nr)
> +{
> + pte_t pte, tmp_pte;
> +
> + pte = ptep_modify_prot_start(vma, addr, ptep);
> + while (--nr) {
> + ptep++;
> + addr += PAGE_SIZE;
> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
> + if (pte_dirty(tmp_pte))
> + pte = pte_mkdirty(pte);
> + if (pte_young(tmp_pte))
> + pte = pte_mkyoung(pte);
> + }
> + return pte;
> +}
> +#endif
> +
> +/* See the comment for ptep_modify_prot_commit */
> +#ifndef modify_prot_commit_ptes
> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, unsigned long addr,
> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
> +{
> + for (;;) {
> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
> + if (--nr == 0)
> + break;
> + ptep++;
> + addr += PAGE_SIZE;
> + old_pte = pte_next_pfn(old_pte);
> + pte = pte_next_pfn(pte);
> + }
> +}
> +#endif
> +
> /*
> * On some architectures hardware does not set page access bit when accessing
> * memory page, it is responsibility of software setting this bit. It brings
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