linux-kernel - Re: [RFC PATCH 09/16] mm/memory: split non-tlb flushing part from zap_page_range

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Message-ID: <7rnj5pt7uaftvvf6sqge4vowvcht7n4cqb4hxh3o6kzxtqumqi@p7ugsoqh6iiz>
Date: Thu, 6 Mar 2025 10:45:01 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: SeongJae Park <sj@...nel.org>
Cc: "Liam R. Howlett" <howlett@...il.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, David Hildenbrand <david@...hat.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, kernel-team@...a.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 09/16] mm/memory: split non-tlb flushing part from
 zap_page_range_single()

On Wed, Mar 05, 2025 at 10:16:04AM -0800, SeongJae Park wrote:
> Some of zap_page_range_single() callers such as [process_]madvise() with
> MADV_DONEED[_LOCKED] cannot batch tlb flushes because
> zap_page_range_single() does tlb flushing for each invocation.  Split
> out core part of zap_page_range_single() except mmu_gather object
> initialization and gathered tlb entries flushing part for such batched
> tlb flushing usage.
> 
> Signed-off-by: SeongJae Park <sj@...nel.org>
> ---
>  mm/memory.c | 36 ++++++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index a838c8c44bfd..aadb2844c701 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2011,38 +2011,46 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
>  	mmu_notifier_invalidate_range_end(&range);
>  }
>  
> -/**
> - * zap_page_range_single - remove user pages in a given range
> - * @vma: vm_area_struct holding the applicable pages
> - * @address: starting address of pages to zap
> - * @size: number of bytes to zap
> - * @details: details of shared cache invalidation
> - *
> - * The range must fit into one VMA.
> - */
> -void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
> +static void unmap_vma_single(struct mmu_gather *tlb,
> +		struct vm_area_struct *vma, unsigned long address,
>  		unsigned long size, struct zap_details *details)
>  {

Please add kerneldoc for this function and explicitly specify that tlb
can not be NULL. Maybe do that in the patch where you make it
non-static.