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 34C9BCAC5A5 for ; Thu, 25 Sep 2025 10:33:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8E4D28E0013; Thu, 25 Sep 2025 06:33:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8BC578E0001; Thu, 25 Sep 2025 06:33:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 820248E0013; Thu, 25 Sep 2025 06:33:19 -0400 (EDT) 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 746858E0001 for ; Thu, 25 Sep 2025 06:33:19 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 15361C0432 for ; Thu, 25 Sep 2025 10:33:19 +0000 (UTC) X-FDA: 83927410518.19.BBFCBD5 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf20.hostedemail.com (Postfix) with ESMTP id 61CC81C000B for ; Thu, 25 Sep 2025 10:33:17 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of dev.jain@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=dev.jain@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1758796397; 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; bh=zX56vZQh6ddO29l8CTyATJ0DBEdvf0QQ4/NcvsRny1g=; b=iOgAn40/hSsfrSZ0T6tfXTw8yWzZqlQgow3XnKqpYWyqVQSTzaB07K9d5Y5D5Qpo+esAlK CGl4EysMKGM758kMz7T6dEtVgJAZBcCnjOEcYL1xpXZfUmBCLbQwq7IF7zWPOUzTZS6Wj9 MxOIwJA0ggWZSn6wlct9DM8adSQ8mgM= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of dev.jain@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=dev.jain@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1758796397; a=rsa-sha256; cv=none; b=VYIvomc1MWUGoUVzHuaxRSOME06zkAvmvsu+lo/5YsJZLeaB1GbMPHjrGNtntXztYyqs3x BpI3NJXMm5OiXpH9ralVkEWgTuTGnsKzI8w2SM/MyyQSfHeTUXR3RNtPvhDZ0aneoUWy9O 6cCDoV9OaUuWVSt3bz1ogza+sqNkyPQ= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 37F0B1692; Thu, 25 Sep 2025 03:33:08 -0700 (PDT) Received: from [10.164.18.52] (MacBook-Pro.blr.arm.com [10.164.18.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 701BB3F694; Thu, 25 Sep 2025 03:33:13 -0700 (PDT) Message-ID: <45e08ee0-c85e-469e-a3eb-4ca2e8b7ec0c@arm.com> Date: Thu, 25 Sep 2025 16:03:10 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: move rmap of mTHP upon CoW reuse To: David Hildenbrand , akpm@linux-foundation.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lokesh Gidra References: <20250925085429.41607-1-dev.jain@arm.com> <072b8684-47fe-4a2a-bf69-f6d348f0489b@redhat.com> Content-Language: en-US From: Dev Jain In-Reply-To: <072b8684-47fe-4a2a-bf69-f6d348f0489b@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 61CC81C000B X-Rspamd-Server: rspam05 X-Stat-Signature: 6q4supcg75bp7aqnqughakn346z86wg7 X-Rspam-User: X-HE-Tag: 1758796397-614812 X-HE-Meta: U2FsdGVkX1/qYS54/h7qT8xUf4muMkx+TlgOqAJX8qzcoUOn8SMvA+YTM6oJuzowSu8sqmNN+6G/IZV7rPLISeRxJeM5kkZ01QIucrTIx/vfE0sGgu7NbglG0UK5FE5BA56x9FiSJRLnYWXOh5hSvtwmqF/evLu9eNiWzTXYhsPSzof1JYewGP540cItwsrGliSJqhLBdwcsOk2czwX2AgqQ5Bi/7rb+BCqIsaOITHttHJjpp07EGJwE1gyJCzE9k5sgv5ULN+VbgSLXlrFSPdCxk1b7NO/H4zfkPbJdOIhZHdvansqz4ezK0eRZ2EcUGpg36QWBq78n1WSBMWhy+8TTR9p6z+e0HF9Ho4pDVqP4RCgGVUddMF8Xvv34bmq83l09Jrao/GGlGD6+cZECj4scdgffspkGoGQKdUHza1J2Xoi8F55ogTiR6QQUoPNCIKzA0VRe5uoIOBHW/foHDHt5tm0v3p7XS3vwCmqevcE7owU5ylNRPhnquEl1LSMsZMe5Kq+P6acg+oI2L9Dcm8OLMRJzoEFMN1u34lLB8a9tNMy7a9xcN7jO9CUjTc6/g/zGzOdbIClepM9sMgXTQO3DHV7Lhs2ZVVuydXxBbcILGnt8FzsJkYbOUX63Ue1SIvf6dSyW+66OeKi5rcqsMsAbG04iGM5rVGDXINmzVZVbBSFMLHtV8cT7Mlay/zsAYUVMnWcdQM5ophvzgIpr5oFjfhqlc418qkPeInLNzYOYqPKi4IVpeHmLuCxmbTTL4k8e1IHrmqY6aaQ2bfSMGwiI9CkOlxn981haWpIZCdb1SsBRdcXGNERQ63wjO7G9M46XgTrbucBbqWszk49zMWKrMwVrmz1QrXvcLZuqEwT/Qo5A8K8Qr4QA/XKukaIMu4gZjE18CSEvlxwUt+qcATaflOCGSPJLKiMjBWYPea/d7hHx3A2z8rNQEgceDY0paLjkuTfeqy5zfsVeNvS z3tQNTw0 98SIN9mvWdMHe9k4LgL5tkmo3kVggSfBz2ufWQ3xQP3FJ3NWhD84JHsF6Kma+wGQe/YsrsZwF2NUhukMCYRqNasgkqWz8XyNcWeQdj9aasjvyQ3GrVxmtcUTj23bRXyqr8K2mczg5mBfIddo= 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 25/09/25 2:46 pm, David Hildenbrand wrote: > On 25.09.25 10:54, Dev Jain wrote: >> At wp-fault time, when we find that a folio is exclusively mapped, we >> move >> folio->mapping to the faulting VMA's anon_vma, so that rmap overhead >> reduces. This is currently done for small folios (base pages) and >> PMD-mapped THPs. Do this for mTHP too. > > I deliberately didn't add this back then because I was not able to > convince myself easily that it is ok in all corner cases. So this > needs some thought. Thanks for your detailed reply. > > > We know that the folio is exclusively mapped to a single MM and that > there are no unexpected references from others (GUP pins, whatsoever). > > But a large folio might be > > (a) mapped into multiple VMAs (e.g., partial mprotect()) in the same MM I think we have the same problem then for PMD-THPs? I see that vma_adjust_trans_huge() only does a PMD split and not folio split. > [--- snip ---] >