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[2003:d8:2f23:9c00:d1f6:f7fe:8f14:7e34]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e752238760sm1503339f8f.34.2025.09.09.00.57.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Sep 2025 00:57:36 -0700 (PDT) Message-ID: <789863b8-dff2-4fe7-b708-7b0c65c7b843@redhat.com> Date: Tue, 9 Sep 2025 09:57:35 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/6] mm: folio_may_be_lru_cached() unless folio_test_large() To: Hugh Dickins , Andrew Morton Cc: Alexander Krabler , "Aneesh Kumar K.V" , Axel Rasmussen , Chris Li , Christoph Hellwig , Frederick Mayle , Jason Gunthorpe , Johannes Weiner , John Hubbard , Keir Fraser , Konstantin Khlebnikov , Li Zhe , Matthew Wilcox , Peter Xu , Rik van Riel , Shivank Garg , Vlastimil Babka , Wei Xu , Will Deacon , yangge , Yuanchu Xie , Yu Zhao , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <41395944-b0e3-c3ac-d648-8ddd70451d28@google.com> <57d2eaf8-3607-f318-e0c5-be02dce61ad0@google.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 09.09.25 00:23, Hugh Dickins wrote: > mm/swap.c and mm/mlock.c agree to drain any per-CPU batch as soon as > a large folio is added: so collect_longterm_unpinnable_folios() just > wastes effort when calling lru_add_drain[_all]() on a large folio. > > But although there is good reason not to batch up PMD-sized folios, > we might well benefit from batching a small number of low-order mTHPs > (though unclear how that "small number" limitation will be implemented). > > So ask if folio_may_be_lru_cached() rather than !folio_test_large(), to > insulate those particular checks from future change. Name preferred > to "folio_is_batchable" because large folios can well be put on a batch: > it's just the per-CPU LRU caches, drained much later, which need care. > > Marked for stable, to counter the increase in lru_add_drain_all()s > from "mm/gup: check ref_count instead of lru before migration". > > Suggested-by: David Hildenbrand > Signed-off-by: Hugh Dickins > Cc: > --- Acked-by: David Hildenbrand -- Cheers David / dhildenb