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t=1787851443; bh=BjfGfa7gS4D2wDK9mCCSlkjUdk96fAt8iFKlJ66xdXk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=EzLpiBjNYRL+cecuiQoLhAzu7P8qyHCBg5rZkgBcp23SnYHYI83dN1J3k3hnXWUun sf5NLBe4/3OssrfnO52PXIBY48h6Xl9YhU1d7FCXkCP2aLD0U1fdzcIBv3WdqSgFIz hjadHXoPzSbMVpUQiJ+eVBHaNsUAcC6l+ka6F9DHPXTRCtvOgwIhoh0mup9ELuSwDL MfL8FqK5PMcINwus6FEHP6gldl8wXFCgjAYaKrMo2JcyUVvoFRvoOWZfcgT/LyrVJu 9tcvciVYTK+I3cB2kbcTTqpwx3p1mK4QvoFlxEMKppupZfkHiMpFIOMhFXMGViy5Lu 9L8/+h48xIwDA== Message-ID: <7fb30b85-ea60-45bd-aef2-494943b524a0@kernel.org> Date: Thu, 27 Aug 2026 19:23:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/25] mm/fbatch: remove !CONFIG_SMP special case of folio_activate() To: Hugh Dickins , Andrew Morton Cc: Ackerley Tng , Alexander Viro , Baolin Wang , Barry Song , Binbin Wu , Christian Brauner , Christoph Hellwig , Christoph Lameter , Claudio Imbrenda , JP Kobryn , Jan Kara , Jens Axboe , Johannes Weiner , Kairui Song , Kiryl Shutsemau , Lance Yang , Leonardo Bras , Lorenzo Stoakes , Marcelo Tosatti , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michal Hocko , Minchan Kim , Muchun Song , Oscar Salvador , Peter Zijlstra , Qi Zheng , Rik van Riel , Sebastian Andrzej Siewior , Shakeel Butt , Suren Baghdasaryan , Vlastimil Babka , Yang Shi , Yu Zhao , Zach O'Keefe , Zi Yan , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <14a16945-529b-8bc0-ab38-3ea97e54e223@google.com> <3f18ab7d-c12a-d2a3-4d3e-f9908f94f27d@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 025BB80006 X-Stat-Signature: n3p1zckpa1g1jqfs3xsmhs4cyqzc8xbj X-HE-Tag: 1787851443-117093 X-HE-Meta: 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 2Xj+M+N6 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/24/26 15:52, Hugh Dickins wrote: > 3.0 commit eb709b0d062e ("mm: batch activate_page() to reduce lock > contention") brought in an ifdef CONFIG_SMP around activate batching: > https://lore.kernel.org/linux-mm/20100805140755.501af8a7.akpm@linux-foundation.org/ > shows a sensitivity to bloat that day, not any incompatibility with UP. > > No other batching here has a UP alternative, and it's a bit confusing: > simplify mm/folio.c a little by removing it now. > > Certainly we can reduce UP bloat (and/or 32-bit bloat) by, say, lowering > FOLIO_BATCH_SIZE from 31: traditionally 16, 14, 15, then raised to 31 by > 6.9 commit 9cecde80aae0 ("mm: increase folio batch size"); or by giving > just the static per-cpu folio batches a type of their own with a smaller > array size on UP (1? or a little batching worthwhile even on UP?). But > not right now, it's orthogonal to this series. > > And I suspect that the old ifdef led to lru_activate being placed last, > whereas it's usually the second most popular fbatch: move it there, to > match cpu_needs_drain() comment "Check these in order of likelihood that > they're not zero". > This fits the theme of removing CONFIG_SMP conditionals where they are not really warranted and cause maintenance overhead. Let's see if this actually creates real problems we have to worry about. Acked-by: David Hildenbrand (Arm) -- Cheers, David