From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F75FC79FA1 for ; Tue, 8 Sep 2026 11:55:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3E0466B0092; Tue, 8 Sep 2026 07:55:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B78E6B0096; Tue, 8 Sep 2026 07:55:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2CDDA6B0098; Tue, 8 Sep 2026 07:55:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id EDC886B0092 for ; Tue, 8 Sep 2026 07:55:05 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 8A97E405F0 for ; Tue, 8 Sep 2026 11:55:05 +0000 (UTC) X-FDA: 85190438970.01.1C956B0 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf09.hostedemail.com (Postfix) with ESMTP id C011014000B for ; Tue, 8 Sep 2026 11:55:03 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=O3u+q7i6; spf=pass (imf09.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788868503; b=Mc69RblWeqS+XsTgYpTUmHuU8dr0zums+XAWBUt8eocPV/iurMM0HbJJoDXMVeRmcg8EAa uoPXuE7F6e2eZypVr4j/Vi+4wqqYv1yi56K3/AK9dBYssRYG1ZWrMVlEEXUNm5HSNtPVbX kSAKFO2h7XN3jGY5DQlIEDCGKOPDDMo= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=O3u+q7i6; spf=pass (imf09.hostedemail.com: domain of vbabka@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=vbabka@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788868503; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=A8fGRJH1FYroE0NYq5pSQ/cdoutdIPA6KQGFv2lno1c=; b=QoM4PuPMFz3vKiDxTWrp3smp/1us1vHpmZV3DUs9XenCwnBEwXMFvyvYMRit6cmVm0jNBJ 9HECD4gtNsZCYmej49mRaBLlmIFqXSoC+FudEJx2M+MZttxs7PtiyJoAZJT4fS1XJs1IVx dxZt5tovT+SIBNVr8rtpQeXMRYKbKPs= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 3F1AC601DB; Tue, 8 Sep 2026 11:55:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A4B91F00A3A; Tue, 8 Sep 2026 11:54:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788868503; bh=A8fGRJH1FYroE0NYq5pSQ/cdoutdIPA6KQGFv2lno1c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=O3u+q7i6QeyYtTqdVxTUmL8k11LRAGHiZTHWhr6k+T3QWv6q7uS4HDzW9FXq1Vocr SfFiOd7fqggCnDd2KFkF97idrc43LCaE5VM4g73AC4KFodCx9IS8NVTRZ1KwUon5dx sOPyvNX1DYrdEcKIRct65bFM1sBOPHn1EK5RaRsYsZLLxKPMV52QrFC2VPhVP+HAGW wtRPwv0O3QLICXC6EzOUSW6JiBETKuWAGceK1oJLhtLPEK0ku3vozxteWTTI3oeqid wTKMiFWoWF95fUnjr0pHc3MnXao3Wsq4WWSN979SZ3M7GC0Ay8nzXRdbC638/yfE27 7hZMc/MF618PQ== Message-ID: Date: Tue, 8 Sep 2026 13:54:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm: remove min_free_kbytes adjustment for THP Content-Language: en-US To: Nimrod Oren , Andrew Morton , David Hildenbrand , Lorenzo Stoakes Cc: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Hugh Dickins , Nirmoy Das , Dragos Tatulea , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260901190123.3511535-1-noren@nvidia.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260901190123.3511535-1-noren@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C011014000B X-Stat-Signature: x8qcs6ino4iwqnfwr83zg3xpnqg9zphs X-HE-Tag: 1788868503-315673 X-HE-Meta: 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 7RPvCpqI AYGcTkceO7Bo2uz4xLHtKTJiVs8mnF2fYhdE74KS4upFCvKJkbmXPKB2rSBmAIX4TGCW6oD7qM73tOqFf7fJlMC2UUuUKxUA52r2wcqANxO1+TaTejg2O9TVNk5mpKXx1hDzEFT69BN5yz6zqqCWkOQB5QUrWFwxcJdeSfU0SdOoOoRGomoo/cC/EzFSgNGWkOV0ap/qKS1jK0gae1U1ykksySEJznsc5b8tskFPMTGv/hx7bG6Adkf/FCeUIvMhKZK01+ZPGgl+7sbwNzptYgU1jkLhCRMESVMIF6lnjJz+ou/b7sqOp0z99zfq5XpXg0hquWO9j/0CtKEnmC9C/zig7at0VM+k+L45sImZAjxZUKmeU0N88puyc+dfDvZXXnWUqIvFkXWowWVNINKdFWBZRFg4tjgiu5rFo Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/1/26 21:01, Nimrod Oren wrote: > When THP is enabled, set_recommended_min_free_kbytes() may raise > min_free_kbytes using a heuristic that scales with pageblock_nr_pages. > Commit f000565adb77 ("thp: set recommended min free kbytes") added this > heuristic to help keep pageblocks free and reduce fragmentation for THP > allocations. > > The recommendation scales poorly with larger base page sizes. With the > default arm64 pageblock sizes, the contribution per eligible zone > before applying the existing cap of 5% of low memory is: > > 4 KiB pages: 2 MiB pageblock, 22 MiB per zone > 16 KiB pages: 32 MiB pageblock, 352 MiB per zone > 64 KiB pages: 512 MiB pageblock, 5.5 GiB per zone > > Even with that cap, min_free_kbytes can reach excessive levels. > > The automatic min_free_kbytes increase predates proactive compaction > and many subsequent changes to compaction. Given those changes, > increasing min_free_kbytes for THP by default is no longer clearly > justified. > > Remove set_recommended_min_free_kbytes() and all associated > recalculation paths. With this policy gone, min_free_kbytes is > controlled only by the page allocator's default calculation and the > vm.min_free_kbytes sysctl. Users who want additional headroom may set a > higher value via that sysctl. > > Link: https://lore.kernel.org/r/20260831075635.2244437-1-noren@nvidia.com/ > Suggested-by: Michal Hocko > Signed-off-by: Nimrod Oren > --- > v3: > * Replace the 1 GiB cap with removal of the THP-driven min_free_kbytes > increase as suggested by Michal. > * Remove all associated recalculation paths. > * Make min_free_kbytes, user_min_free_kbytes, > calculate_min_free_kbytes(), and setup_per_zone_wmarks() static. > * Drop the now-unused declarations and khugepaged's page_alloc.h include. > * Drop the obsolete v2 documentation addition. > > v2: > * Use a named constant for the cap. > * Drop explicit linux/sizes.h include. > * Update min_free_kbytes documentation. > https://lore.kernel.org/r/20260831075635.2244437-1-noren@nvidia.com/ > > v1: > * Cap the final recommendation at 1 GiB as suggested by Lorenzo. > https://lore.kernel.org/r/20260728202014.2517142-1-noren@nvidia.com/ > > RFC v1: > https://lore.kernel.org/r/20260716173504.760369-1-noren@nvidia.com/ > --- > include/linux/khugepaged.h | 5 ---- > mm/huge_memory.c | 14 --------- > mm/internal.h | 8 ----- > mm/khugepaged.c | 60 -------------------------------------- > mm/page_alloc.c | 11 +++---- > mm/page_alloc.h | 2 -- > mm/shmem.c | 7 ----- > 7 files changed, 4 insertions(+), 103 deletions(-) Given neither of the patchset versions achieved universal acceptance, could we try just disabling all the automatic (re)calculations of min_free_kbytes the first moment the sysctl gets adjusted from userspace?