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 B1793CCF9E3 for ; Tue, 11 Nov 2025 03:25:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1D6648E000E; Mon, 10 Nov 2025 22:25:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1ADE18E0002; Mon, 10 Nov 2025 22:25:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0EB638E000E; Mon, 10 Nov 2025 22:25:04 -0500 (EST) 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 008968E0002 for ; Mon, 10 Nov 2025 22:25:03 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 8637F13AA2C for ; Tue, 11 Nov 2025 03:25:03 +0000 (UTC) X-FDA: 84096884886.12.DAC30A7 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) by imf13.hostedemail.com (Postfix) with ESMTP id C98B62000F for ; Tue, 11 Nov 2025 03:25:01 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ogFJes54; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.189 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1762831502; a=rsa-sha256; cv=none; b=KE8C9i67aXnWsuezgt/32TOvEl8g3kLwa0D5p8G4+ChZbTdzr4NftMQCWu2Eny2RrasOmq PHlyqIF2kV7gH/I/FOCOZMI2RUSdHN0KA/31EhcVDwpELTwOuFc3yswtKIcMgg3EtDk02s osAxp+aO5XaznR2JWTszbZy8MGuorfg= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ogFJes54; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf13.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.189 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=1762831502; 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=HakIRat1LMkIofrDpBtAbKRxMTQrzWYviIUr8PQmSMQ=; b=puYLB4LKS7/CU6W3644DA+P/8BpC0q7Z8gQuI60HXeKnzumaEnAXG8VEMb9ebVKRKld7cB 3iNmNseFSHhmTTpacPTjdDcQmD7Quye+mjOKPwxPqTLH2sDQRV61tlEY2KoTVQlTPO/P5v jIt+6kpMrM4K3/Dvj6ONRc2rx9KWsw0= Message-ID: <1a6dfda1-380d-4e6b-af72-4e6257838c08@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1762831500; 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=HakIRat1LMkIofrDpBtAbKRxMTQrzWYviIUr8PQmSMQ=; b=ogFJes54pFGN05g+xE+mxRKl0VVn+YgldSLppe95wFlyb9aBoDjP+jF+JbbB1/Q27r7zkF YEawhKNCho3YnnN0yEOB5fjIk9iM8KO0D5HOr5PC8rt+yhSwKVoiQ7IggLJr1XK99JhtrJ dprOCkMUeB3Gj3cHItXB2SOg41/a2z8= Date: Tue, 11 Nov 2025 11:24:37 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v1 04/26] mm: vmscan: refactor move_folios_to_lru() To: Shakeel Butt Cc: Harry Yoo , hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, muchun.song@linux.dev, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-rt-devel@lists.linux.dev References: <97ea4728568459f501ddcab6c378c29064630bb9.1761658310.git.zhengqi.arch@bytedance.com> <366385a3-ed0e-440b-a08b-9cf14165ee8f@linux.dev> <2a68bddf-e6e6-4960-b5bc-1a39d747ea9b@linux.dev> <8d6655f8-2756-45bb-85c1-223c3a5e656c@linux.dev> <646pwrc7sxan6wlwndjyu7upx32fkd7bv5vqlut3tjt65eeyby@23efyxvpg2nx> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <646pwrc7sxan6wlwndjyu7upx32fkd7bv5vqlut3tjt65eeyby@23efyxvpg2nx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: C98B62000F X-Rspamd-Server: rspam07 X-Stat-Signature: 7ixoip3nt5fbwiwxjsraaas58yrugkq7 X-Rspam-User: X-HE-Tag: 1762831501-711241 X-HE-Meta: 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 HPcXr1/T cfWrDrxDAtFlBthyEfb88qaizc08hwXEKwSoJhmb7xjQ8O6VxdbP+J2RQagcdscUGXDdK/m8fzrMzve1wyBK23fq8yh0+x7x64ZEsMOUbCEQLvuu5jZ1NcoA6P5NZe0fNqxQTNbiPiVYJp+pzZ4QMEAEeBBERWAdnNX+WvgjtAe9A8ccnD7/yRSG/9oFSVFFG8ryVkzkdTSMoa34iLiGbrvi2JqpKJJAis/rEM6HlX/1adxDQgJDvooM5YmOHf11pTWXV 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 11/11/25 11:17 AM, Shakeel Butt wrote: > On Tue, Nov 11, 2025 at 11:04:09AM +0800, Qi Zheng wrote: >> >> On 11/11/25 12:47 AM, Shakeel Butt wrote: >>> On Mon, Nov 10, 2025 at 02:43:21PM +0900, Harry Yoo wrote: >>>> On Mon, Nov 10, 2025 at 12:30:06PM +0800, Qi Zheng wrote: >>>>>> Maybe we could make it safe against re-entrant IRQ handlers by using >>>>>> read-modify-write operations? >>>>> >>>>> Isn't it because of the RMW operation that we need to use IRQ to >>>>> guarantee atomicity? Or have I misunderstood something? >>>> >>>> I meant using atomic operations instead of disabling IRQs, like, by >>>> using this_cpu_add() or cmpxchg() instead. >>> >>> We already have mod_node_page_state() which is safe from IRQs and is >>> optimized to not disable IRQs for archs with HAVE_CMPXCHG_LOCAL which >>> includes x86 and arm64. >> >> However, in the !CONFIG_HAVE_CMPXCHG_LOCAL case, mod_node_page_state() >> still calls local_irq_save(). Is this feasible in the PREEMPT_RT kernel? >> > > Yes we can disable irqs on PREEMPT_RT but it is usually frown upon and > it is usually requested to do so only for short window. However if Got it. > someone running PREEMPT_RT on an arch without HAVE_CMPXCHG_LOCAL and has > issues with mod_node_page_state() then they can solve it then. I don't > think we need to fix that now. OK. >