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=1794598877; b=qXq+74ULe1bgYwomFhN9jjzrICmUBjGE2KeErIjaxqzkts4xkRVGrzRdjkP9GWzN0GME WPQi8Fq40YvoKm9QpvsZRo5KwjLjLihXG/0Sl4mSvooAf4C8F2Yfpdl5Kh+WzmhGeRzox 89put4b3zfjoJHSUNt4O22YoQvELU9Wrfo0pX+oZr4UB6mMvZ3o4YrCUNGkCulMkPo3+d RfHSY3/zmHJPG826TGq2oy+Rx6NnXxvbHfc6UO+yKhNUwgr9I3Ugu/BEZfjY6Eg7BKux4 glzeaGdUvrVKCPvwgByPr+yKuP7ZyXsQxfhf4hAfXs1UUf5sz5y7vEYC2qPHcgzFiUg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794598877; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=tmAxQe7kqdr9fp5dnRxl5XhH9VmvJBdZ5/nN3KtZcKk=; b=sP6Dp2RDXvyXHOGos53wL0hFKMA7vC6eiadri6PYeIreO4pO1o/iamTmX9BvTNNxpN8y I5FYwtqcjAhTmTgPncGMWTIZad1qJ5CTq5nMZxJMN2iOA913a4VEHdCTs+nfjH8FuXLTH eEZtazAyMgqjKn8SG3umteI5Ao274VVvFzOh8GZkbBnRwEmzcCTol+dpbEJbwL4WG1IQB afMEVES1Cn4BinDH7iRgKynGy4wv2dO2SM7MB5BMr9n0QrWsqZk8kHYCZC2GwNf5k3OUE aCeXAgUunjebGBC3PGBGSVjYQORVIzAOApAn42P9doM4JVd0bcnb+cJDr9RF69n0LBQ== 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=tjVdpTNm; 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 37710606A331 for ; Fri, 13 Nov 2026 19:41:16 +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=tjVdpTNm Received: by smtp.kernel.org (Postfix) with ESMTPSA id B26691F000C4; Fri, 13 Nov 2026 19:41:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1794598876; bh=tmAxQe7kqdr9fp5dnRxl5XhH9VmvJBdZ5/nN3KtZcKk=; h=Date:To:From:Subject; b=tjVdpTNmpvhuSPc4r6KqIP3WkucfwHXXJUvLUKsI4zDJrXPbpPzZzi95rpkJNyFX/ LzCNG0rDQ6LtmPSyTiUQplnfpJ6b+9/cCdEvsdrTz4Lzol86+m1DwsVHHAzWuz4/3Z qnivAW0rpaXfDFSRCCoQyr4YTvdQj9krBqUhf6zE= Date: Fri, 13 Nov 2026 11:41:16 -0800 To: mm-commits@vger.kernel.org,kasong@tencent.com,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch removed from -mm tree Message-Id: <20261113194116.B26691F000C4@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 quilt patch titled Subject: mm/mglru: lift youngest gen protection for higher priority has been removed from the -mm tree. Its filename was mm-mglru-lift-youngest-gen-protection-for-higher-priority.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Kairui Song Subject: mm/mglru: lift youngest gen protection for higher priority Date: Thu, 12 Nov 2026 07:25:55 +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->min_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/20261111232603.9934-9-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 --- 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 @@ -4774,12 +4774,14 @@ 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