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 B4373D711D5 for ; Mon, 22 Dec 2025 04:00:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2326A6B0088; Sun, 21 Dec 2025 23:00:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1B6616B0089; Sun, 21 Dec 2025 23:00:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0C20D6B008A; Sun, 21 Dec 2025 23:00:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id F13F76B0088 for ; Sun, 21 Dec 2025 23:00:04 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id A7F72B983E for ; Mon, 22 Dec 2025 04:00:03 +0000 (UTC) X-FDA: 84245753886.05.7F53DD6 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) by imf20.hostedemail.com (Postfix) with ESMTP id AB7071C0004 for ; Mon, 22 Dec 2025 04:00:01 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=g6v2xQ7M; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1766376002; a=rsa-sha256; cv=none; b=X5j05Mr43MM2pwznyvhZYu2PWdZd/SdPDasOS43WmvsmBimEUgzooO9BYNKWl13bkR9o0b WJd/5OXDOMmoORRahxmWduoU0Cxqa9K7f2NES34LkRULV68Im4daPRP7oSkabtSDTYb1PX jhsHCgNkpJpl8abUgQJ1eslkFc9Pl/Q= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=g6v2xQ7M; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf20.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.174 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1766376002; 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=oMAUFbvixYMyej2RaSYfA1urQk5c5I28T+hhpcsE9H0=; b=eKL/Y1km37mRaj88b7DnRcJ1w84a39KmWJ08Ee64JxZKhAKFWWCnwvaxCAst0uw5WFhvFz bhZqg/KyfGwVN6iYwcAuwug2DiCW84hdb0H7XERKlPTS+qnonh2dLnQDUPHtnCLnZ5GEvN dd38BLEomzwU+M9z5sKJ6oqc+Y8iUaU= Message-ID: <646b9414-baf6-4278-b4df-5f4abeca5e67@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1766375996; 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=oMAUFbvixYMyej2RaSYfA1urQk5c5I28T+hhpcsE9H0=; b=g6v2xQ7M8QO66aigU0pLALSMnoZMrAa0ibLD6yQBpo955FlVEJHREynjUrmcTOE07I8f0P kpM7NEgztyVHuj9o+us7wsmmttYuoj6+q3bQ6rdT/yygYGfMGCeh5Mgad3knDvZ3QfhA0T Y6t6WGSMh9/TudxQzDc1wnao7Oa/uWg= Date: Mon, 22 Dec 2025 11:59:46 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2 27/28] mm: memcontrol: eliminate the problem of dying memory cgroup for 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, Muchun Song , Qi Zheng References: 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-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: AB7071C0004 X-Stat-Signature: jsxn1rdz81ghyrn63d4i871c6ckjow8k X-Rspam-User: X-HE-Tag: 1766376001-67334 X-HE-Meta: U2FsdGVkX19jD4VxXJTB/Y7ANJ+6d2p8er8JePZaEvTYi04uc75jiWC0Y2xnCpu1CNmLavyYG9zZTiZO89jzUtC3nA18AS2BEocbPe9XvyK7kexTTO1YYSe8RWztbkgMIsgP1ip5z2xxJrVMHKhaZ2LXOd5Wj2LdM0wHKtBJ0I+wUVCHkhH3uIF+Ueh01/azVJS4yT+duEEmMDno/aGWzR1+OWpXIE9USZdtBWF0swZFtU28NOn3FBAvjWQ4uGSiFIkKjUXokaOcOC7CgLpOSz25oQZhWkj20dq+ehsjsaMiVHktasW+b8BCvTMwe1ViqGgpJQnaf7+i9xXKwI3Gb595Q8FuoBSDoWDvJRtHOua/bOsY7pvloiB/N4clLDpGeAvdYLHaFbRYGjSpkTiJlBZPwY7wLKLEnXGqWIWhP9Y+rWIHFBaoc27Tbk2zt04etHHAg4FtYhETJ36tLVj68LY+ZRpjXbLrRU7ZNOloyHhZH5ba6cnMSNiszPOF31BLLCQxWnJmfQpc3nPBUF49aQdoPQHAKo7gnYI5o95tAUel5KM1LOBx+xtYSZDlwJnLbSeLnhgc09Bg79ERePmSw/U6ooiYbdnwvSKjj19CawM41QSfz6KxQ1yRNxpk7j6SMiNT7ixX7eneHndzkOfevtIFcK/WNm0L0xP/pkz9EcSCj2R/+5U4mGmpLCdrJL6ygVCaJPITzpgtwCBPeE0sfwnO5qoC+GakU+I0esvGLyU0CXrDQ8slZrq9GC+7kOj93J1YjH15VX4mAKAi2qh2AQwTDu/uET7jLg304GlKsSFoADmHphAGy5Ycob+G/UgEr0qL4CieWKqbyesiOTy+KYfdSukH4XTCVzbiDqeumtcpF3ZZVsNQ4sVmcjJoSr9Ve8wFti2SkiZC8IZVT5ch6hIaHXncSgFDykfRuBQCxYULT+/DHqiTBHgFb8VtxhglTKxErglKhF+4CNClV9x 0JZUm6G8 Hd4Od6dUVmIvDhaj8fP2iPEFSpT5AWsAKEIm7BviKiriSggiq0Uyvp+t34hLrcMDr2uHsTkt+jqhseuCENrwr0ooyao3LVsfGD5AXtT9pEUI6kEZVyvWSJ6DHv9xTAYAWIdYDYLv+7PonloG7gnHPQl9le99YPKtNy0HZ/dYh7BdAbEjZV3aP9yoJjAMdnVC8ic3WqWPqHtXy9WVMMCMjHJU4rvxlHm7f6KowLgH4ApfgTiA= 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 10:06 PM, Johannes Weiner wrote: > On Wed, Dec 17, 2025 at 03:27:51PM +0800, Qi Zheng wrote: >> From: Muchun Song >> >> Pagecache pages are charged at allocation time and hold a reference >> to the original memory cgroup until reclaimed. Depending on memory >> pressure, page sharing patterns between different cgroups and cgroup >> creation/destruction rates, many dying memory cgroups can be pinned >> by pagecache pages, reducing page reclaim efficiency and wasting >> memory. Converting LRU folios and most other raw memory cgroup pins >> to the object cgroup direction can fix this long-living problem. > > This is already in the coverletter. Please describe here what the > patch itself does. IOW, now that everything is set up, switch > folio->memcg_data pointers to objcgs, update the accessors, and > execute reparenting on cgroup death. Got it, will do. > >> Finally, folio->memcg_data of LRU folios and kmem folios will always >> point to an object cgroup pointer. The folio->memcg_data of slab >> folios will point to an vector of object cgroups. > >> @@ -223,22 +223,55 @@ static inline void __memcg_reparent_objcgs(struct mem_cgroup *src, >> >> static inline void reparent_locks(struct mem_cgroup *src, struct mem_cgroup *dst) >> { >> + int nid, nest = 0; >> + >> spin_lock_irq(&objcg_lock); >> + for_each_node(nid) { >> + spin_lock_nested(&mem_cgroup_lruvec(src, >> + NODE_DATA(nid))->lru_lock, nest++); >> + spin_lock_nested(&mem_cgroup_lruvec(dst, >> + NODE_DATA(nid))->lru_lock, nest++); >> + } >> } > > Looks okay to me. If this should turn out to be a scalability problem > in practice, we can make objcgs per-node, and then reparent lru/objcg > pairs on a per-node basis without nesting locks. > >> static inline void reparent_unlocks(struct mem_cgroup *src, struct mem_cgroup *dst) >> { >> + int nid; >> + >> + for_each_node(nid) { >> + spin_unlock(&mem_cgroup_lruvec(dst, NODE_DATA(nid))->lru_lock); >> + spin_unlock(&mem_cgroup_lruvec(src, NODE_DATA(nid))->lru_lock); >> + } >> spin_unlock_irq(&objcg_lock); >> } >> >> +static void memcg_reparent_lru_folios(struct mem_cgroup *src, >> + struct mem_cgroup *dst) >> +{ >> + if (lru_gen_enabled()) >> + lru_gen_reparent_memcg(src, dst); >> + else >> + lru_reparent_memcg(src, dst); >> +} >> + >> static void memcg_reparent_objcgs(struct mem_cgroup *src) >> { >> struct obj_cgroup *objcg = rcu_dereference_protected(src->objcg, true); >> struct mem_cgroup *dst = parent_mem_cgroup(src); >> >> +retry: >> + if (lru_gen_enabled()) >> + max_lru_gen_memcg(dst); >> + >> reparent_locks(src, dst); >> + if (lru_gen_enabled() && !recheck_lru_gen_max_memcg(dst)) { >> + reparent_unlocks(src, dst); >> + cond_resched(); >> + goto retry; >> + } >> >> __memcg_reparent_objcgs(src, dst); >> + memcg_reparent_lru_folios(src, dst); > > Please inline memcg_reparent_lru_folios() here, to keep the lru vs > lrugen switching as "flat" as possible: > > if (lru_gen_enabled()) { > if (!recheck_lru_gen_max_memcgs(parent)) { > reparent_unlocks(memcg, parent); > cond_resched(); > goto retry; > } > lru_gen_reparent_memcg(memcg, parent); > } else { > lru_reparent_memcg(memcg, parent); > } Looks better, will change to this style. > >> @@ -989,6 +1022,8 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) >> /** >> * get_mem_cgroup_from_folio - Obtain a reference on a given folio's memcg. >> * @folio: folio from which memcg should be extracted. >> + * >> + * The folio and objcg or memcg binding rules can refer to folio_memcg(). > > See folio_memcg() for folio->objcg/memcg binding rules. OK, will do.