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 9E137C9830E for ; Thu, 24 Sep 2026 19:50:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 54F816B0088; Thu, 24 Sep 2026 15:50:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 528586B008A; Thu, 24 Sep 2026 15:50:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4170B6B008C; Thu, 24 Sep 2026 15:50:19 -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 F078E6B0088 for ; Thu, 24 Sep 2026 15:50:18 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 5A3BC1A0165 for ; Thu, 24 Sep 2026 19:50:18 +0000 (UTC) X-FDA: 85249697316.26.8EE6A2D Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf02.hostedemail.com (Postfix) with ESMTP id 7ED5280011 for ; Thu, 24 Sep 2026 19:50:16 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=MjHBmkcQ; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790279416; 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=R7GRre8UKUgbIjQqpBFebYRVHyGQlunCInkDxKufszI=; b=ZbC9uyj+doWxz5EAX7AUyGHwhcjvjUUMFzC0dzvNK8NVwDqwomkWCDebweg2pi9Vy4OPqG brRcSkCVC9YKJ+onjdZByHGC1XKEbjF/55m60X0Zmm36m+DDS/KI+4onNYMyNY4ByFk+VC 6utVvWa/S6i1WVM0GMTnSJ4vlLaIQ9Q= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=MjHBmkcQ; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790279416; b=2icjVM8xiznfZfXBAfdVp9QlEE2y0vFIIjGP6gqF5TP+/raYz184mh8WVh7n4Rku8/r8br 04Ang2WP5m1YK9711MwxyyufpU4X2sYXXAjjPV/OGLThdTEusRgw3AAns7cHFDxC/Zv0r7 Mc+H6IzIda3eZK0Wdz5k7i+M2qdEL+s= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id AF9CA40670; Thu, 24 Sep 2026 19:50:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 453CB1F000FF; Thu, 24 Sep 2026 19:50:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790279415; bh=R7GRre8UKUgbIjQqpBFebYRVHyGQlunCInkDxKufszI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=MjHBmkcQ/qd9t49haNxYHlTYpGVQk37oxGdxBtQQZoCApRCZIkkpIH62vPL3/Hkz4 +y3DiPqZ3dq0Cw37qn86Jgoisgo6S07xcFsmhtTC5ViMb7uRJ7PjwZho/fEDnfEO4j RgEJYQhP27rF5OGwAOMOp/i3S6x4y5NL6oAhY6AacCRC/++DowaWH4hOj0dDRE6cwJ 4KMhXGS665+F63XbcZEv9Q6qa4Zq1Oka5xIOZmsDNu8ZB4EKwwd4xJXzl14TZ06BuI XTW7jfK5RqrUgQhUeuIe9IJGy+nE8bc6SNuOaQX9CyOUx0/++A+FJM/0rMpkIg+Geb 7z3+Pr2a8Ut8Q== Message-ID: Date: Thu, 24 Sep 2026 21:50:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/5] mm: sub-folio dirty tracking for PTE-mapped mmap writes To: Kiryl Shutsemau , akpm@linux-foundation.org, "Matthew Wilcox (Oracle)" Cc: Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jan Kara , Rik van Riel , Harry Yoo , Lance Yang , Jann Horn , Alexander Viro , Christian Brauner , "Darrick J. Wong" , Carlos Maiolino , Usama Arif , Pedro Falcato , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, "Kiryl Shutsemau (Meta)" References: <20260903182943.662461-1-kirill@shutemov.name> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260903182943.662461-1-kirill@shutemov.name> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 3fjqto3droecdz4ofzb5cmdhg7fmrgia X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7ED5280011 X-HE-Tag: 1790279416-734908 X-HE-Meta: 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 qkEPrOmy K7/Lq75foUvHMy2gyv6JFlKwg4ydM6lr79uDJLVKZuRxaWdWy7EDZVfXWIyK6s2i4B8oFuLs8mhXmwwq6F9fpCbQtXS2E1Yy3+dwqLvV5Ur6HhZmAFyZcDeVgYOBr3MpAxzkfb3toLuMB2Jb55Z5dffJnntYGvFLem845A5HJI2ZWhGgXKsx6DmTrAcDugehN0s8kKx2hSmvHBDvnotdAmq7csxLXNuD6ckum3rroWgQ0X1P/ZRF6mHIYSuR8D05rD3A+cmxyBd1avCLc52yEbWsRIsVZIpe+e9TI Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/3/26 20:29, Kiryl Shutsemau wrote: > From: "Kiryl Shutsemau (Meta)" > > A store through a shared file mapping dirties the whole folio. With large > page cache folios that turns a 4K store into 2M of writeback: one dirty > bit per folio, and writeback has no way to know which part changed. > > XFS already knows better. iomap tracks dirty state per block and > iomap_writeback_folio() submits only the dirty ranges, and the buffered > write path sets just the range it copied. Only the mmap path throws that > away, because iomap_dirty_folio() covers the whole folio. > > Narrowing the dirtying at page_mkwrite() time does not work on its own: > set_pte_range() batch-maps a whole folio writable on the first shared > write fault, so the stores that follow never fault and never reach the > filesystem. > > So harvest the hardware instead. folio_clear_dirty_for_io() already calls > folio_mkclean(), whose rmap walk reads pte_dirty() for every entry of the > folio and throws it away. Those bits are the only record of which parts > of a large folio were written through a mapping. Collect them there and > hand the filesystem the runs that were dirty, through a new > a_ops->dirty_folio_range(). > > All of this is about PTE-mapped folios. A PMD-mapped folio has a single > dirty bit for the 2M it maps, so there is nothing finer to harvest, and > it keeps writing back whole. Keeping shared write faults off PMDs is a > separate patch and not part of this posting. > > On a 512M file in 2M folios on XFS, storing one byte per folio and > calling msync() wrote 512M before and writes 1M after, with identical > minor fault counts. Just a note that with things like cont-pte we see the trend that we only have a single logical dirty bit for the entire coalesced PTE. Similar to having only a single dirty bit for a PMD-mapped THP. -- Cheers, David