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Message-ID: <af5d1332-bbcc-4110-a167-84f2bb592794@redhat.com>
Date: Tue, 30 Jan 2024 10:08:53 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>, Ryan Roberts <ryan.roberts@....com>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
Nick Piggin <npiggin@...il.com>, Peter Zijlstra <peterz@...radead.org>,
Michael Ellerman <mpe@...erman.id.au>,
Christophe Leroy <christophe.leroy@...roup.eu>,
"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>, Arnd Bergmann <arnd@...db.de>,
linux-arch@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org
Subject: Re: [PATCH v1 9/9] mm/memory: optimize unmap/zap with PTE-mapped THP
Re-reading the docs myself:
> +#ifndef get_and_clear_full_ptes
> +/**
> + * get_and_clear_full_ptes - Clear PTEs that map consecutive pages of the same
> + * folio, collecting dirty/accessed bits.
> + * @mm: Address space the pages are mapped into.
> + * @addr: Address the first page is mapped at.
> + * @ptep: Page table pointer for the first entry.
> + * @nr: Number of entries to clear.
> + * @full: Whether we are clearing a full mm.
> + *
> + * May be overridden by the architecture; otherwise, implemented as a simple
> + * loop over ptep_get_and_clear_full(), merging dirty/accessed bits into
> + * returned PTE.
"into the"
> + *
> + * Note that PTE bits in the PTE range besides the PFN can differ. For example,
> + * some PTEs might be write-protected.
> + *
> + * Context: The caller holds the page table lock. The PTEs map consecutive
> + * pages that belong to the same folio. The PTEs are all in the same PMD.
> + */
> +static inline pte_t get_and_clear_full_ptes(struct mm_struct *mm,
> + unsigned long addr, pte_t *ptep, unsigned int nr, int full)
> +{
> + pte_t pte, tmp_pte;
> +
> + pte = ptep_get_and_clear_full(mm, addr, ptep, full);
> + while (--nr) {
> + ptep++;
> + addr += PAGE_SIZE;
> + tmp_pte = ptep_get_and_clear_full(mm, addr, ptep, full);
> + if (pte_dirty(tmp_pte))
> + pte = pte_mkdirty(pte);
> + if (pte_young(tmp_pte))
> + pte = pte_mkyoung(pte);
> + }
> + return pte;
> +}
> +#endif
> +
> +#ifndef clear_full_ptes
> +/**
> + * clear_full_ptes - Clear PTEs that map consecutive pages of the same folio.
> + * @mm: Address space the pages are mapped into.
> + * @addr: Address the first page is mapped at.
> + * @ptep: Page table pointer for the first entry.
> + * @nr: Number of entries to clear.
> + * @full: Whether we are clearing a full mm.
Something went missing:
May be overridden by the architecture; otherwise, implemented as a
simple loop over ptep_get_and_clear_full().
--
Cheers,
David / dhildenb
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