linux-kernel - Re: [PATCH v3 4/9] mm: introduce skip_none

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Message-ID: <c7eeac93-3619-4443-896f-ef2e02f0bef0@redhat.com>
Date: Thu, 14 Nov 2024 09:04:48 +0100
From: David Hildenbrand <david@...hat.com>
To: Qi Zheng <zhengqi.arch@...edance.com>, jannh@...gle.com,
 hughd@...gle.com, willy@...radead.org, muchun.song@...ux.dev,
 vbabka@...nel.org, akpm@...ux-foundation.org, peterx@...hat.com
Cc: mgorman@...e.de, catalin.marinas@....com, will@...nel.org,
 dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
 x86@...nel.org, lorenzo.stoakes@...cle.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, zokeefe@...gle.com, rientjes@...gle.com
Subject: Re: [PATCH v3 4/9] mm: introduce skip_none_ptes()


>   static unsigned long zap_pte_range(struct mmu_gather *tlb,
>   				struct vm_area_struct *vma, pmd_t *pmd,
>   				unsigned long addr, unsigned long end,
> @@ -1682,13 +1704,17 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
>   		pte_t ptent = ptep_get(pte);
>   		int max_nr;
>   
> -		nr = 1;
> -		if (pte_none(ptent))
> -			continue;
> -
>   		if (need_resched())
>   			break;
>   
> +		nr = skip_none_ptes(pte, addr, end);
> +		if (nr) {
> +			addr += PAGE_SIZE * nr;
> +			if (addr == end)
> +				break;
> +			pte += nr;
> +		}
> +
>   		max_nr = (end - addr) / PAGE_SIZE;

I dislike calculating max_nr twice, once here and once in skip_non_ptes.

Further, you're missing to update ptent here. If you inline it you can 
avoid another ptep_get().

>   		if (pte_present(ptent)) {
>   			nr = zap_present_ptes(tlb, vma, pte, ptent, max_nr,


-- 
Cheers,

David / dhildenb