linux-kernel - Re: [PATCH 2/2] mm: mincore: use folio_pte

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Message-ID: <Z-UtOF97qjcm4Hgu@localhost.localdomain>
Date: Thu, 27 Mar 2025 11:49:28 +0100
From: Oscar Salvador <osalvador@...e.de>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org,
	david@...hat.com, 21cnbao@...il.com, ryan.roberts@....com,
	ziy@...dia.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: mincore: use folio_pte_batch() to batch process
 large folios

On Wed, Mar 26, 2025 at 11:38:11AM +0800, Baolin Wang wrote:
> @@ -118,16 +120,31 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  		walk->action = ACTION_AGAIN;
>  		return 0;
>  	}
> -	for (; addr != end; ptep++, addr += PAGE_SIZE) {
> +	for (; addr != end; ptep += step, addr += step * PAGE_SIZE) {
>  		pte_t pte = ptep_get(ptep);
>  
> +		step = 1;
>  		/* We need to do cache lookup too for pte markers */
>  		if (pte_none_mostly(pte))
>  			__mincore_unmapped_range(addr, addr + PAGE_SIZE,
>  						 vma, vec);
> -		else if (pte_present(pte))
> -			*vec = 1;
> -		else { /* pte is a swap entry */
> +		else if (pte_present(pte)) {
> +			if (pte_batch_hint(ptep, pte) > 1) {

AFAIU, you will only batch if the CONT_PTE is set, but that is only true for arm64,
and so we lose the ability to batch in e.g: x86 when we have contiguous
entries, right?

So why not have folio_pte_batch take care of it directly without involving
pte_batch_hint here?

-- 
Oscar Salvador
SUSE Labs