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 F1493CCFA18 for ; Tue, 11 Nov 2025 03:23:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4E0D28E0007; Mon, 10 Nov 2025 22:23:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4B8228E0002; Mon, 10 Nov 2025 22:23:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F5088E0007; Mon, 10 Nov 2025 22:23:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 324338E0002 for ; Mon, 10 Nov 2025 22:23:51 -0500 (EST) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id D289012CDF7 for ; Tue, 11 Nov 2025 03:23:50 +0000 (UTC) X-FDA: 84096881820.20.6791213 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) by imf05.hostedemail.com (Postfix) with ESMTP id 13852100002 for ; Tue, 11 Nov 2025 03:23:48 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=UPsgop1U; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.177 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=1762831429; 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=dRsaTINzsimOU7sZV8eoCiJrcZgmp+6Lp0gB2Wv5aQA=; b=ppmo3ITufjn7HTmUoOZ09M1jX1yJQsztXENQKvWRt/kcxQjEzi4M/S+7O1emglDpnigJ1j e6DADD8/TWy30gnsMXtM3+Wgn0Y9ade3W3sxu1lsaEdiNQTWrQKlzNGSx+h0Dchc9YOJO/ cHZjhQqwKuKJCJcuzqjfRJDI0Cdpwsg= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1762831429; a=rsa-sha256; cv=none; b=UYMlZnewaLl7xlBqBpWk+pD18JfvrVAI8//N0cdUmWtAEJxzF2Lmha5+C8atxSLeH9YYmi jYSXo8sN6AebestVc5Luk/POyz//G9Q/fO0rvubd2QW07ydESuT9GAPOP9qSugRB6ejx6N ZXOROi3Z4GzJuJdYsPvwJ0NXg69GDVI= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=UPsgop1U; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf05.hostedemail.com: domain of qi.zheng@linux.dev designates 91.218.175.177 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev Message-ID: <8ee2e132-6f80-4da5-a03d-820e4031a9fc@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1762831426; 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=dRsaTINzsimOU7sZV8eoCiJrcZgmp+6Lp0gB2Wv5aQA=; b=UPsgop1UdM6iVCJKMcwkLQQY5vs0SziOL+3tJ/VISeF+lny1aY3cMPROrx3D8xU1Knz0m9 plXApivp7nUGBs1nBOpcQsteaD4gZ2IUmuGCzVATmlxxRxRqknAme7SMVjU/wDvlKfS9zp TplEvHow7j+IYgpq+bQVD88BJ3XJbYM= Date: Tue, 11 Nov 2025 11:23:33 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v1 04/26] mm: vmscan: refactor move_folios_to_lru() To: Harry Yoo Cc: Shakeel Butt , 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> 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: p76qprhk9okmz9x6ar81si5rhjw1wap4 X-Rspam-User: X-Rspamd-Queue-Id: 13852100002 X-Rspamd-Server: rspam10 X-HE-Tag: 1762831428-615909 X-HE-Meta: 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 7iNGRP39 YpkkwiK9pCE6i7f2ek08ZeFxhgHer5PNz67WZITyMtTnOlBQ/Qpt2tUbj2li3WLqzEUYvoY8Ov0z57sUhLmpBAwPOONngKuI+d1CcpAlCqq4vOTEq3KlQz85l2//IlLWTJ292j8q7uj0UiUVehZQ/mO9EiQSZZlPEC4FQ/cbS3AOBXWtIapFk77bojdcfPaeCJQYKpcjhmlmqUMQEy4MOXrWMoI1u+D5MSPcZJcuOJW9BqzDJVcDpAVEprvtHwma4dIke 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 11:16 AM, Harry Yoo 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? > > Hmm I was going to say it's necessary, but AFAICT we don't allocate > or free memory in hardirq context on PREEMPT_RT (that's the policy) > and so I'd say it's not necessary to disable IRQs. > > Sounds like we still want to disable IRQs only on !PREEMPT_RT on > such architectures? > > Not sure how seriously do PREEMPT_RT folks care about architectures > without HAVE_CMPXCHG_LOCAL. (riscv and loongarch have ARCH_SUPPORTS_RT > but doesn't have HAVE_CMPXCHG_LOCAL). > > If they do care, this can be done as a separate patch series because > we already call local_irq_{save,restore}() in many places in mm/vmstat.c > if the architecture doesn't not have HAVE_CMPXCHG_LOCAL. Got it. I will ignore it for now. > >>> Let me send the patch to cleanup the memcg code which uses >>> __mod_node_page_state. >