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 DA52ECCD1A7 for ; Tue, 21 Oct 2025 06:22:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 40A938E000B; Tue, 21 Oct 2025 02:22:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3E1FC8E0002; Tue, 21 Oct 2025 02:22:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3216F8E000B; Tue, 21 Oct 2025 02:22:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 1B8518E0002 for ; Tue, 21 Oct 2025 02:22:24 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id BD5F511A019 for ; Tue, 21 Oct 2025 06:22:23 +0000 (UTC) X-FDA: 84021126966.18.2AE94AD Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) by imf17.hostedemail.com (Postfix) with ESMTP id 8A1004000A for ; Tue, 21 Oct 2025 06:22:21 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=QM6xEaXQ; spf=pass (imf17.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.184 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=1761027741; 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=kya1JAQmVRbw00lv1IpjiwWxKFwn52KaWMDi202LPPQ=; b=gniJW0m2braaeL1yERiqSPRxJ1IoiRt50g0JQNRgr8l135jxKCOgfPIL8/k8EkRekEvldV X0jSTnxvspNJDPAjqcpvQ+TuSCbpjhoo2nS+y0oVrjg7Pa+lApvMJB0QBAyGPPHWLGjQoF cIHmnzTqZrR0kpZP1YQhj6CrXDOu/i8= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=QM6xEaXQ; spf=pass (imf17.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.184 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=1761027741; a=rsa-sha256; cv=none; b=OkTNx9XW25RMhv8PUrMUIuDDiHcpkCaxnimThN5n+LeWSDQeU+eCDeMDjAscXgwG4Dtx3P PR3c04Bedz6du3WyuH1E4CjHY0mOJh6ly6DI4WRG3Q6fr+4pS4VxaumjPjDQeVnBRUAz3U lCiW2sYyZ6LBzf/7mUm1rk0q7uDBQyc= Message-ID: <3acbf7df-b890-4679-bbbe-959bd45fdef3@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761027739; 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=kya1JAQmVRbw00lv1IpjiwWxKFwn52KaWMDi202LPPQ=; b=QM6xEaXQ1k9fTRzqU35722oyvtkjOhFRFUn6hv7F15sVNnUzXmeTTn2sd0kuiqZ03eqLb3 yeUPqfOeX+rbw3/za/8SnDe/EQgKFudCqn0bA8eG/3HY1aYPpOdEgHLGz3PCveOq0oGoVK 1/6Xk2/3qrqGrJgsLddULhG7FS2cUmc= Date: Tue, 21 Oct 2025 14:21:55 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v5 4/4] mm: thp: reparent the split queue during memcg offline To: Harry Yoo Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Qi Zheng References: <645f537dee489faa45e611d303bf482a06f0ece7.1760509767.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: bmewb3wr6bsg9qggciq6545n8qhco7zm X-Rspamd-Queue-Id: 8A1004000A X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1761027741-304880 X-HE-Meta: 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 ZWykuOs+ jPaKON+8q0X+Xxvv4VsG9gulgVKCQ9TA8aJNHYr3pHmjBkDplZC1hZ4zl5EsiuWiVlUgxsKGRvPNuw3N6z/FGFkJ4HyRlDoCz2rHUaC0vF6VgXoYpOuMCNgcTUlq5RqIN9uxrF1B4r3sMj0yvSk4s+Zmrzih/V264v98TrshsYxWvQghnrS+DKI28ncq2VP8IXEEKrh2OFmaQv2cghiPBWd/oLSRuMLeUkP2DdbFnYLdpcBC0UyZ7GSbRl4g8IPp9kpctvWgpdhUb4320NOc9N86QqN3l9Ctfusb7sloC2/ZQ4XGI+ZZk5vmPoA== 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 10/21/25 2:09 PM, Harry Yoo wrote: > On Wed, Oct 15, 2025 at 02:35:33PM +0800, Qi Zheng wrote: >> From: Qi Zheng >> >> Similar to list_lru, the split queue is relatively independent and does >> not need to be reparented along with objcg and LRU folios (holding >> objcg lock and lru lock). So let's apply the similar mechanism as list_lru >> to reparent the split queue separately when memcg is offine. >> >> This is also a preparation for reparenting LRU folios. >> >> Signed-off-by: Qi Zheng >> Acked-by: Zi Yan >> Reviewed-by: Muchun Song >> Acked-by: David Hildenbrand >> Acked-by: Shakeel Butt >> --- > > Looks good to me, > Reviewed-by: Harry Yoo Thanks. > > with a question: > >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index e850bc10da3e2..9323039418201 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1117,8 +1117,19 @@ static struct deferred_split *split_queue_lock(int nid, struct mem_cgroup *memcg >> { >> struct deferred_split *queue; >> >> +retry: >> queue = memcg_split_queue(nid, memcg); >> spin_lock(&queue->split_queue_lock); >> + /* >> + * There is a period between setting memcg to dying and reparenting >> + * deferred split queue, and during this period the THPs in the deferred >> + * split queue will be hidden from the shrinker side. >> + */ > > You mean it will be hidden if the shrinker bit is not set for the node > in the parent memcg, right? Look at the following situation: CPU 0 CPU 1 ----- ----- set CSS_DYING deferred_split_scan /* * See CSS_DYING, and return the parent * memcg's ds_queue. But the pages on the * child memcg's ds_queue has not yet been * reparented to the parent memcg, that is, * it is hidden. */ --> ds_queue = split_queue_lock_irqsave() reparent_deferred_split_queue Thanks, Qi >