linux-kernel - Re: [PATCH v4 6/6] mm: madvise: Avoid split during MADV_PAGEOUT and MADV

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Message-ID: <ffeee7da-e625-40dc-8da8-b70e4e6ef935@redhat.com>
Date: Fri, 15 Mar 2024 11:35:05 +0100
From: David Hildenbrand <david@...hat.com>
To: Ryan Roberts <ryan.roberts@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Matthew Wilcox <willy@...radead.org>, Huang Ying <ying.huang@...el.com>,
 Gao Xiang <xiang@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
 Yang Shi <shy828301@...il.com>, Michal Hocko <mhocko@...e.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Barry Song <21cnbao@...il.com>,
 Chris Li <chrisl@...nel.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/6] mm: madvise: Avoid split during MADV_PAGEOUT and
 MADV_COLD

> -		if (!pageout && pte_young(ptent)) {
> -			ptent = ptep_get_and_clear_full(mm, addr, pte,
> -							tlb->fullmm);
> -			ptent = pte_mkold(ptent);
> -			set_pte_at(mm, addr, pte, ptent);
> -			tlb_remove_tlb_entry(tlb, pte, addr);
> +		if (!pageout) {
> +			for (; nr != 0; nr--, pte++, addr += PAGE_SIZE) {
> +				if (ptep_test_and_clear_young(vma, addr, pte))
> +					tlb_remove_tlb_entry(tlb, pte, addr);
> +			}
>   		}


The following might turn out a bit nicer: Make folio_pte_batch() collect 
"any_young", then doing something like we do with "any_writable" in the 
fork() case:

..
	nr = folio_pte_batch(folio, addr, pte, ptent, max_nr,
			     fpb_flags, NULL, any_young);
	if (any_young)
		pte_mkyoung(ptent)
..

if (!pageout && pte_young(ptent)) {
	mkold_full_ptes(mm, addr, pte, nr, tlb->fullmm);
	tlb_remove_tlb_entries(tlb, pte, nr, addr);
}

-- 
Cheers,

David / dhildenb