From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D072641F5D5; Thu, 27 Aug 2026 17:24:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787851444; cv=none; b=GLNmndFHvT7hMA4LFoLAPYq1yOKQRaQGFBcpIqk3m/+B4Tko8yLd+57QUleBCSdykKu8R0BVZOBNEWaPqcFNXRc3Nz35jLNlqDZvE9TyujW1031OH11smtS/ITumAgIaAmgf19wN0rh0orhvB5wuGMkoBdrM7v19QhryHA+TG6A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787851444; c=relaxed/simple; bh=H5ZRMIE38fbrqt3mKWehWW9NwT08Qp2Sc2+mr9vS/as=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uMdx21Ywj2lkbjkW4VZxumdUJZ9xex+j5iyMQGHwf92a0M1VGCxYoNOxrxeT3etBUNP64zp8Xh1ws9L1vOsYQUxGgP4rfb7uiMCMtamBNixRnCPKeGj2To/dTAa6t2bc2Mk/skiJ+iGQTHYTejRPKHwmXCoJTk6fMufpIPuJoHA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EzLpiBjN; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EzLpiBjN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B14011F000E9; Thu, 27 Aug 2026 17:23:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; 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 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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