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 3B11AD711D5 for ; Mon, 22 Dec 2025 03:55:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9ADF06B0089; Sun, 21 Dec 2025 22:55:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 983CB6B008A; Sun, 21 Dec 2025 22:55:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8BB1E6B008C; Sun, 21 Dec 2025 22:55:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7D2396B0089 for ; Sun, 21 Dec 2025 22:55:24 -0500 (EST) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 2FD3260A16 for ; Mon, 22 Dec 2025 03:55:24 +0000 (UTC) X-FDA: 84245742168.15.7543579 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) by imf21.hostedemail.com (Postfix) with ESMTP id 48D3B1C000A for ; Mon, 22 Dec 2025 03:55:22 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Y5bED2PI; spf=pass (imf21.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.188 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766375722; 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=2xqiag8fioZOe9NX9oHRHaDgP//h6CBY1O8QvNdZ/XU=; b=WoSDhVi638doaNyj3V9Ne94gbDq6Wzh3/i2bjCf4wUZCRY57EM0Cte38Ud+pwMS4ymf5N5 JqlYHtm63epU+JQ2d7xtGjbnDXuoEhyQ4jJkBwaoVTYyXL9zL+8yWlsb7Kz4OOF1h9kxQy FLFWwbRwzJADgJmenPhlbsjjOckTADg= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=Y5bED2PI; spf=pass (imf21.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.188 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766375722; a=rsa-sha256; cv=none; b=pWWs7uOBbsu14/eqbDJCfrfcJiii1wmj8enOhWalSJ1XLhRXdHOkRxWlw4fkMqScfgoYDE Tfr0yQrVdrTAzWBHMxPAGsUjufPc6I/9m/x+3RNbp/MR8s03WwIDaH6pV2uB/PffFNzRoY da58MceHaZslVKSQknVYhtZAsMKi3RM= Message-ID: <00f47523-e458-4e9e-8354-1c33bf0591b8@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766375715; h=from:from: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; bh=2xqiag8fioZOe9NX9oHRHaDgP//h6CBY1O8QvNdZ/XU=; b=Y5bED2PIdjRswHhz5ri86a3xuzcsAPrgnCBsf4HQ2FgRrsukkrTd76VX+FYh4x8wwvB3mB Fp0g52FAQ4i9IXYKS3Wfsv3Z/gRuJqfBuAroC+gLllj/yblELd8z0vYQDuJxl3RR9vHMIb vIkXAJSjU0i86jfI3sXnHuPHndBX8mM= Date: Mon, 22 Dec 2025 11:55:01 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 24/28] mm: vmscan: prepare for reparenting traditional LRU folios To: Johannes Weiner Cc: hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng References: <800faf905149ee1e1699d9fd319842550d343f43.1765956026.git.zhengqi.arch@bytedance.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: ib5roktsikrxenfqir1owztcc9e67y5u X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 48D3B1C000A X-HE-Tag: 1766375722-141973 X-HE-Meta: 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 qMtYWEiZ 67FhJrcsdioXj6aQIsz0l7sf0H4vEAu/1jAy3jTZ/65gF7uh2Xs1M/Avcoluy3ZG6zyf1gF9niGZPJXyBA9fdlY/NIN1mmyciq6yBmVdLegEUFiIWdcENHPGsskwyIEwgll5fLDHDZcTdY1P7978BBG8cmwvH0PUXwvPcQu3SVrbmwF+mJp+Wak1qXpUS0nmTYBAwU1jbk9h/C7lmztjTzxUN3ChEFPSrlHZJ1Imo1pDK4M2EaCLzd1TzNKnWBPSY+A59jSbZvjuudXu9SXH4F57zlnlm1JGBn7UrYtLLiW7OIO93JjUyMyEEGCgIVtbXPooa X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/18/25 9:32 PM, Johannes Weiner wrote: > On Wed, Dec 17, 2025 at 03:27:48PM +0800, Qi Zheng wrote: >> From: Qi Zheng >> >> To reslove the dying memcg issue, we need to reparent LRU folios of child > > resolve Got it. > >> memcg to its parent memcg. For traditional LRU list, each lruvec of every >> memcg comprises four LRU lists. Due to the symmetry of the LRU lists, it >> is feasible to transfer the LRU lists from a memcg to its parent memcg >> during the reparenting process. >> >> This commit implements the specific function, which will be used during >> the reparenting process. >> >> Signed-off-by: Qi Zheng >> Reviewed-by: Harry Yoo > > Overall looks sane to me. I have a few nits below, not nothing > major. With those resolved, please feel free to add > > Acked-by: Johannes Weiner Thanks! > >> @@ -2648,6 +2648,44 @@ static bool can_age_anon_pages(struct lruvec *lruvec, >> lruvec_memcg(lruvec)); >> } >> >> +#ifdef CONFIG_MEMCG >> +static void lruvec_reparent_lru(struct lruvec *src, struct lruvec *dst, >> + enum lru_list lru) >> +{ >> + int zid; >> + struct mem_cgroup_per_node *mz_src, *mz_dst; >> + >> + mz_src = container_of(src, struct mem_cgroup_per_node, lruvec); >> + mz_dst = container_of(dst, struct mem_cgroup_per_node, lruvec); >> + >> + if (lru != LRU_UNEVICTABLE) >> + list_splice_tail_init(&src->lists[lru], &dst->lists[lru]); >> + >> + for (zid = 0; zid < MAX_NR_ZONES; zid++) { >> + mz_dst->lru_zone_size[zid][lru] += mz_src->lru_zone_size[zid][lru]; >> + mz_src->lru_zone_size[zid][lru] = 0; >> + } >> +} >> + >> +void lru_reparent_memcg(struct mem_cgroup *src, struct mem_cgroup *dst) > > I can see why you want to pass both src and dst for convenience, but > it makes the API look a lot more generic than it is. It can only > safely move LRUs from a cgroup to its parent. > > As such, I'd slightly prefer only passing one pointer and doing the > parent lookup internally. It's dealer's choice. Make sense, will do. > > However, if you'd like to keep both pointers for a centralized lookup, > can you please rename the parameters @child and @parent, and add > > VM_WARN_ON(parent != parent_mem_cgroup(child)); > > Also please add a comment explaining the expected caller locking. OK. > > Lastly, vmscan.c is the reclaim policy. Mechanical LRU shuffling like > this is better placed in mm/swap.c. OK, will move it to mm/swap.c.