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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772096895; bh=y11g85XCUlJsP2pyz2TMzKQd4wTjpzRaV9t1RrP34Is=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fz2NDguc1AOocd74h8/J/h7ht36vcblPdeyl1ZjskZ7ogkSk1JEeX1JSL2GS/wXMD 6/3VKmcLGkdTHvpkKnUlhY73qSQgkI5UMSA6TGcPqpCL0tKrQUGPgodhruXcwy/clE 93idkfQEhc3SibeIbHqrEUcxXp8pfLXx8QYAq78BeGCktAGudCKsWyRE4AiL0GO8ev cLqSWYlL/AjfUAzOViDYpfJSWLs1xCAE9r6rP5XeufpTYz0/WRlB8AbtvUE/7v4qDC Uu0PjfRGzRPH0v0yfeKQrnUKcz22mqwEiAXAqSAiwctDwofLuelBp+jKmeKvkL1aID OV9ExLj0EQ3kA== Message-ID: <2599bc1e-1f8e-46bc-afea-4cb8f657545b@kernel.org> Date: Thu, 26 Feb 2026 10:08:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/5] mm: support batched checking of the young flag for MGLRU To: Baolin Wang , akpm@linux-foundation.org Cc: catalin.marinas@arm.com, will@kernel.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <84d2426c63c1eafeaa0cfbad7c5cc11e9c11b980.1771897150.git.baolin.wang@linux.alibaba.com> <2e7a1e24-3616-4b79-b943-b5f7efde2d31@kernel.org> <0871edb9-08a2-46a0-ade6-af842a12e0d3@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: aa37xj5bukqkcgrujrcmjhcm17p6jfpg X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4C9EE4000D X-HE-Tag: 1772096896-600181 X-HE-Meta: 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 cIeeDres 44rgtgggHPGv0bcZE8JnJYQcasRmO3VOBF3m3iXmSOGKDoQFrlvUz/Dph0x+fsif7y/Ai4QzIt9+zuqst8AS/bu56OMUCfw2YpnfntgOhILAS+K1VCrSFOJJKDf/PliX41ChX78L2/ImI/4YTilgN/nPp61W/AUNxMnJ02b8YholKxAULsmJJVe3xp4ZBm78r+c1WU0H+frltFrHMNWV/8lHP8ASZBoV/4ooUnH6cs77oaVi87T740pYStgGXF9yFdWjYPt6kqqiKM3fqh7pMC+zWl+EcnZS6oz28 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> >>> +            pte_t pteval = ptep_get(pvmw.pte); >> >> I wonder if there could be a way to avoid this ptep_get() by letting >> page_vma_mapped_walk() just provide the last value it used (in >> check_pte() I guess). Something for another patch. > > Well, we’d need to add a new field to ‘struct page_vma_mapped_walk’ to > store the last value (e.g., pvmw.pteval), Yes. > but this makes me wonder if it > is worth adding a new field just to avoid a lightweight read (which > should have no obvious performance impact). You recall that ptep_get() on arm64 is not that lightweight due to con-pte? :) But yeah, something for another day. [...] >> >> What is "batched"? Did you mean "nr_ptes" ? Or just the initial value >> for "nr" ? > > There is already an 'nr' variable in this function. "nr_ptes" sounds > good to me, and will use it. You can just use "nr" here and reuse it for the existing variable? Both have the same semantics (nr of ptes / pages), so having a single value might cause less confusion. -- Cheers, David