From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4C4D560A6F4F for ; Fri, 13 Nov 2026 18:56:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=I1kRu6x5 Received: by kanga.kvack.org (Postfix) id 5F38C6B05C5; Fri, 13 Nov 2026 13:56:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5CB1E6B05C6; Fri, 13 Nov 2026 13:56:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 492F06B05C7; Fri, 13 Nov 2026 13:56:33 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 25AD26B05C5 for ; Fri, 13 Nov 2026 13:56:33 -0500 (EST) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 0B05A8022F for ; Fri, 13 Nov 2026 18:56:32 +0000 (UTC) X-FDA: 85431001824.20.10A7858 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf13.hostedemail.com (Postfix) with ESMTP id 59D5B20009 for ; Fri, 13 Nov 2026 18:56:30 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=I1kRu6x5; spf=pass (imf13.hostedemail.com: domain of baohua@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=baohua@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=1794596190; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=g6Eh7AV/JKMXLoOZYMqKzMkw/bKKMbo74UOatYbLA9E=; b=VCQC2YkmfRcph02ahIFbU2RS+rDns1A8tWssRpsZBCGH6evtHgZBmnqb6OJaDs7x6mwsN+ TRzTCLU8L+3jwOz44YT6kQAlrGDHdUr6rnBRcrU1+OdiHMzeuuAfzVTzF7KQaam9O1Yn9n U+3fqxRTg1WLe5lodYdU+kZnqbf/SsU= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1794596190; b=eOaPQWWMEKDH8ydWEY+QsNqw2nbU6EmAZFubwgp/WLA36/EIc5O30Qiv9gFsMjWxo8/zzx OFFuNtuSMb/nip2psVtSmeMsEhDbAlhXRYM+DtF5nFBIMbF1m2Dnue/sH0OZq8OBVe9T8N shCqJZl4onk+rlBH/iGoMIuXrqUs9DA= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=I1kRu6x5; spf=pass (imf13.hostedemail.com: domain of baohua@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=baohua@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id A2D8D400CC; Fri, 13 Nov 2026 18:56:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3B291F000C5; Fri, 13 Nov 2026 18:56:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794596189; bh=g6Eh7AV/JKMXLoOZYMqKzMkw/bKKMbo74UOatYbLA9E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=I1kRu6x5DS/oaFLvEsjQ8qb2eKA/xxW+Vm0JNZ0pKFc2IH3MVbojchyxDot6deHTO wuUZNe0AbVzdLWbMscW9i+zzuJavWjcTOFdV1NBlCwtK9ACxXdyNhfFFc0ombsa7cy ZMAfs2tc7AHwBoluCxpvhCHylkW7MHBzfIA2E5jiv5kYqj3dMg6+GrinpuGm+0wjaD WllZFJ9QWePC05p7TDGtOmO7yzAoNanzKWoKMczLP7qIwl3tFESKF93VV4YxFPofGL QiqISvU5U8poztYgdptbrlykgjWI3pz2rNBcDhs8rRf0W23jAH/6DtN4/raa9ZXnF8 ynQX6qly5SscA== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: axelrasmussen@google.com, baolin.wang@linux.alibaba.com, baoquan.he@linux.dev, hannes@cmpxchg.org, hui.zhu@linux.dev, kasong@tencent.com, kunwu.chan@gmail.com, liam@infradead.org, lianux.mm@gmail.com, linux-kernel@vger.kernel.org, liuxiang.277@bytedance.com, lyugaofei@xiaomi.com, mhocko@kernel.org, mhocko@suse.com, qi.zheng@linux.dev, ridong.chen@linux.dev, rppt@kernel.org, ryncsn@gmail.com, shakeel.butt@linux.dev, surenb@google.com, wangzicheng@honor.com, weixugc@google.com, yuanchu@google.com, zhangbo56@xiaomi.com, zhuhui@kylinos.cn, sidchintamaneni@gmail.com, Barry Song Subject: [PATCH v8 08/16] mm/mglru: lift youngest gen protection for higher priority Date: Sat, 14 Nov 2026 02:55:33 +0800 Message-Id: <20261113185541.70203-9-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20261113185541.70203-1-baohua@kernel.org> References: <20261113185541.70203-1-baohua@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Stat-Signature: bt1rcnnk6afho54iihbpe4ndmdjdw7o9 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 59D5B20009 X-Rspam-User: X-HE-Tag: 1794596190-104950 X-HE-Meta: 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 EH/Mm9Ff EmVnmc2MI0o7YBkK5kJ23N5bSpCBTYKcaoH6Lb40IwM9nUld+B8L/V21aD7J0xh2dCZE2jKgyVJGcOj9wWWSHU3iWmsbTzi2H8/qRk2u6ylkW+0udHD5CH6EhSIHRDOf13jpnT+yfGMpY8kJxjgA7yuMyk9W1abm6mwWvnKgz2IoMpUDyQYAAXevqlEjT8QAyW9Y9D4hkD4uzUql3XLGxKw+lu3IsDNv/ew/E/qcNQqMlFbHYM3y1XTnnQjjoCyOamI3IYRHf94WdeKBQFjj4ukmcRcHTJ6pl6CTVs2hiNB8ylb2y2iKhR4ZlfBmosIkDFwDfHkph94CyntaIFL6HLe+qAv8JXybhKijo Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: Kairui Song 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. Signed-off-by: Kairui Song Signed-off-by: Barry Song (Xiaomi) Reviewed-by: Kunwu Chan --- mm/vmscan.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 8a74e01c2390..8e0972db35da 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4772,12 +4772,14 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, 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; -- 2.39.3 (Apple Git-146)