From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794694248; b=ywAmjqAJ9enxTvZYkwqD8wcmCLrqmwPyx/EUxO4/5mySmDzHuke8px9LNpiQLFldraMJ h8t18lnTVlASZyk2m6OiGGCdFo1IeF1q2hHcKqQPzyORvdSSW6UklY3iHX6Ngcr2TdC6H a7tWfdakFRNPMFbX44GUl/tP2GcNYsY0n/vJ4OUXgD5FDQ9WNOmSCDKDFWgVrxO+MXzsX 2vmNanSMgY91GeoEpd7ia/hzbvSY8/csn3niwVnYquvXDzJXT3v4GV6vE4NGfT+AsKCbo Ic8ws3Qr/BPoo190CpHOQFsD7wmAekYi7beo82KA1i+0MK1EqsgkseysOR2H6Nf3HNA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794694248; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=oQYt97GvkNNNepdgahkKEaBNgp4DCTlAtxVNgKhO+NY=; b=gaVsADVMTv8w1W6xsWYrmyhYkIRbEakfI6Xi6meiWy69D+rH24Ui/oVsgjA7Of9hepwF opKvKsdBmfdTa3RlpHI1gF+1LrlfQFjOPnBXcT4Y2Z1xuOcW7EF9VxDoFtdinUJYBjfft dXi/g1UYUzQjjbNjfdRaidEhI17tayP0sY3LM4KSBnZEHf7uryh4o9Jn/I1k/7tKYw2df JriNEmGmUTLIqUac6XjkwNaMbYaNj8q27KBN1boAS1U7bJRHzGlAChnNTZKUW5qv4dNfa VOeRLjXQBqBy9ggWg+NO69GWyJLhT/TRUyfrEoULWEjPc7ddObAQIcK2dkN+7Xshi7Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b="Zdx/VwGG"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 00001606A32E for ; Sat, 14 Nov 2026 22:10:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=Zdx/VwGG Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E2A01F000C4; Sat, 14 Nov 2026 22:10:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1794694247; bh=oQYt97GvkNNNepdgahkKEaBNgp4DCTlAtxVNgKhO+NY=; h=Date:To:From:Subject; b=Zdx/VwGGf70Vk6fhyDUuAT4rPMuys5QT5nxZi3bZ4m2zHFFrBuJSwzcfDaVmoCQ3N DYjuqKuq+rF9f4fgXufnRgva6OmbjNZ3Y4Lb5vWgTokMzuuJws7ctR9RAZBaE3qS3J bWOvT3WWPJu157VXw1w8qdPArzXmgjEsXSVVuFAQ= Date: Sat, 14 Nov 2026 14:10:47 -0800 To: mm-commits@vger.kernel.org,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch added to mm-new branch Message-Id: <20261114221047.7E2A01F000C4@smtp.kernel.org> X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list The patch titled Subject: mm/mglru: lift youngest gen protection for higher priority has been added to the -mm mm-new branch. Its filename is mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. The mm-new branch of mm.git is not included in linux-next If a few days of testing in mm-new is successful, the patch will me moved into mm.git's mm-unstable branch, which is included in linux-next Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Kairui Song Subject: mm/mglru: lift youngest gen protection for higher priority Date: Sun, 15 Nov 2026 04:07:55 +0800 The forced protection of younger generations contradicts the goal of minimizing the I/O cost of reclaim. Under high memory pressure, MGLRU can repeatedly trigger premature OOMs, while the classic LRU does not. The problem is that aging may fail to keep up with reclaim. When this happens, reclaimers may all abort prematurely because they see only empty generations or just two generations remaining. Proactive aging does not solve this problem either. The number of threads performing proactive aging is limited, while the number of concurrent reclaimers can be much larger. This is a fundamental limitation of MGLRU. One possible solution is to use an aging lock. However, the aging lock introduces significant jitter under heavy memory pressure and has been reported to cause noticeable lags on Android. Furthermore, the generation-based reclaim model can conflict with the goal of swappiness, which is to minimize I/O cost rather than blindly follow folio hotness. The previous commit allowed reclaimers running at non-default priorities to reclaim up to `lrugen->max_seq`, while reclaimers at the default priority could reclaim only up to `lrugen->min_seq`. This patch further refines generation protection based on reclaim priority. At the default priority, reclaimers can reclaim generations down to `lrugen->max_seq - MIN_NR_GENS`. As reclaim priority increases, reclaimers are progressively allowed to reclaim younger generations. With this graduated protection, premature OOMs are no longer observed, while swappiness is also respected. Link: https://lore.kernel.org/20261114200803.23129-9-baohua@kernel.org Signed-off-by: Kairui Song Signed-off-by: Barry Song (Xiaomi) Signed-off-by: Andrew Morton Reviewed-by: Kunwu Chan Cc: Axel Rasmussen Cc: Baolin Wang Cc: Baoquan He Cc: Johannes Weiner Cc: Cc: Liam R. Howlett Cc: wang lian Cc: Cc: Cc: Michal Hocko Cc: Qi Zheng Cc: Ridong Chen Cc: Mike Rapoport Cc: Kairui Song Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: wangzicheng Cc: Wei Xu Cc: Yuanchu Xie Cc: Bo Zhang Cc: Hui Zhu Cc: Siddharth Chintamaneni Cc: Kunwu Chan Cc: Bo Zhang mm/vmscan.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/mm/vmscan.c~mm-mglru-lift-youngest-gen-protection-for-higher-priority +++ a/mm/vmscan.c @@ -4772,12 +4772,14 @@ static int scan_folios(unsigned long nr_ VM_WARN_ON_ONCE(!list_empty(list)); /* - * Respect the gen hotness distribution at low priority to avoid - * aging and scan cost, but prefer to satisfy the reclaimers request - * when under pressure to respect swappiness more and reduce IO cost. + * Respect hotness at default priority, and only reach into the + * newest generation when under severe pressure, so hot folios are + * not evicted as soon as priority is raised. */ if (sc->priority == DEF_PRIORITY) - seq = lrugen->min_seq[type]; + seq = lrugen->max_seq - MIN_NR_GENS; + else if (sc->priority > DEF_PRIORITY / 2) + seq = lrugen->max_seq - 1; else seq = lrugen->max_seq; _ Patches currently in -mm which might be from kasong@tencent.com are mm-mglru-report-evictable-sizes-per-type.patch mm-mglru-extract-lruvec_populated_min_seq-helper.patch mm-mglru-reclaim-from-the-oldest-populated-gen.patch mm-mglru-lift-the-forced-protection-of-reclaimer.patch mm-mglru-skip-zones-above-reclaim_idx-instead-of-rotating-them.patch mm-mglru-return-for-unavailable-anon-reclaim-earlier.patch mm-mglru-balance-anon-and-file-scan-budget-by-refault-rate.patch mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch