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 6D50DC5DF66 for ; Mon, 17 Aug 2026 10:07:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 761006B00AA; Mon, 17 Aug 2026 06:07:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 711D36B00AC; Mon, 17 Aug 2026 06:07:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5B32C6B00AD; Mon, 17 Aug 2026 06:07:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3146A6B00AA for ; Mon, 17 Aug 2026 06:07:17 -0400 (EDT) Received: from smtpin29.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id A9397806DC for ; Mon, 17 Aug 2026 10:07:16 +0000 (UTC) X-FDA: 85110333672.29.24F29EE Received: from flow-b2-smtp.messagingengine.com (flow-b2-smtp.messagingengine.com [202.12.124.137]) by imf14.hostedemail.com (Postfix) with ESMTP id A535C100008 for ; Mon, 17 Aug 2026 10:07:14 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="O bw+j5W"; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=jc5xJb2V; spf=pass (imf14.hostedemail.com: domain of kirill@shutemov.name designates 202.12.124.137 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786961234; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=aRuNgn93bXJUfUxBiQxkO2z074NGsTuHkXM1In4i/2g=; b=nQW7yQwmmgYjzTYe5p58I8H0UuSx2mV1AkHp0haUQEWRh6d6jupVqeuNqXP/RJ5YE2mPIX To9V8NdTxdaI6BeHnfkX5++e8j7e11xbNSwBp9UWJImwBf/yyaEFpsv6VjjxVVQ9WDrjdQ EO1+UlJI4uIY09MqGrfytOR+wST6QjI= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="O bw+j5W"; dkim=pass header.d=messagingengine.com header.s=fm3 header.b=jc5xJb2V; spf=pass (imf14.hostedemail.com: domain of kirill@shutemov.name designates 202.12.124.137 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786961234; b=EAcDM2f0JaGaldj5b6CNAwerjZK7tp3TqkTwMZWedfi+LIM+1jEZ9ls34K7Tws6d1nS7Ai xWHX3Xw47ndIZZe/2ilzFUC6UX0uaNMTYkZhua5kGgRxMngKjoSasxH/8NCzua6JhsbEFT jMoak4Rzqn8RTlm3tLKOhhtn6C6lsmQ= Received: from phl-compute-06.internal (phl-compute-06.internal [10.202.2.46]) by mailflow.stl.internal (Postfix) with ESMTP id 5ECA31300157; Mon, 17 Aug 2026 06:07:12 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-06.internal (MEProxy); Mon, 17 Aug 2026 06:07:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov.name; h=cc:cc:content-type:content-type:date:date:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:subject:subject:to:to; s=fm1; t=1786961232; x= 1786968432; bh=aRuNgn93bXJUfUxBiQxkO2z074NGsTuHkXM1In4i/2g=; b=O bw+j5WgWN+X6RQhGAYltwX6zzKc0Fc3AgF/3bxvz2QdUBFHjnMtBLTcg+Y+dnImg CyzEfKss1yEa2iQcZJvd7MoCY3w8OU/SSX5g8LouAtrJSqf2QgP4o3DVmRU4RfAE xL6WLF8j79qAZvgk0xHb/r+suYpm9YbGpJj3HNbBlXaIFwCjomWvp39d7bu0pE9O FQ7J9brTf0KpLa4NP5We5Yt5jfLeGAcKf8WLpTIrZIz5BEL9gW5R0udM8ieJU8AC 6+tWXw25nO0maJonQZMdrMIZq3EXoX0ev6OqrvgZfzxh6dvU6RvUG977GDJbSb4v 7MjxthZq5Ew36jTVBXhTQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:subject:subject:to :to:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t= 1786961232; x=1786968432; bh=aRuNgn93bXJUfUxBiQxkO2z074NGsTuHkXM 1In4i/2g=; b=jc5xJb2VoVZ1fl2S6LLqziq4i2u2Rbe32OHQeJVp/2ttPYTXew0 7fI87ivUzXyjtnbDs9dM6NQNV3o8ArPMOKaUgnltc5Lub9V598q6WxgipKSq6vty zeDD7M/ZgRR1gOO4hUgeirt736eb0ZwlUwCWnJNZDvk45D3gRHqaNGzzARe++MR9 T8wj+C5TYn88f0zcpQvtazCWS5NJGNTs8rMFuHegFjkZ7AePLSicCWft5HQoGLPo Ln/FnQvW+gGfYcLSaa3nFZzFQoC5+Ljnv2h1n2phwmmvNY7BrTExfOMM6wYBBug/ CEcTRhxwPoeOjpi4FPmH/fDkD7KGYVnvEwQ== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTGPke0xlf6uK3/vVuV73Zp1ci4I00XU/mQfuBGFKH1EChMGX2W2K2Ay2xhloeELQD YiSpOdYfS3z1XRkLC6OwopMYsiHdQ/yeActqocVNoFvfU/5hj7DZTAbsGqeu/+vlYMOKYe MWZ9Q8UiaBU71nzHRAot0umiaedntditcGBLwUem5zhFHFf5OpfS/6n4GvupEXcpjvPGj3 YS/MsMxbcZPoVQjXb4Y5nmgZiQQTorgVnlVV7XtccWjaPbJxsCJxHuas6xK55NYWz1sLxN BrpX30FWPC089z3CGRvQuRihRi+MjBpPadK+XwuOwmXhO/v6SpeTG64SVzAEO1fg3twnP1 Kff7Ds0jl28z1J7Pw/pA2yU9ggaWKCe8j6+zwfuGFFyZuYj9ej/W7PLO9hSwDLHvIdW6e6 Mr/XVT8/uY+izsqEvf9nEEzVsCTyF+Mu7ocLv1N8u1P7CBjqyb9zStDL6Ow8OhJrSPvHnZ CY4gqFI+3SIrPoHTIQjBKp2kK4SlVy31eGOwFfSooL93C7phrDuEtE6RThgrayhp9q/CEb MtROetx8oiqBJOf2mJ2ieygLVtmzuoOpIsCwDXTmS1tO5vJZ8JyienAdNO5QvrPaiK4piA hA0YgweTdo/51rf4vottrOb6FRoIjt2cLXIPrFbDaGaLAA1zaoVYm2Nyd23A X-ME-Proxy: Feedback-ID: ie3994620:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 17 Aug 2026 06:07:10 -0400 (EDT) Date: Mon, 17 Aug 2026 11:07:08 +0100 From: Kiryl Shutsemau To: Zi Yan Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, nico.pache@linux.dev, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, hughd@google.com, lance.yang@linux.dev, liam@infradead.org, mhocko@suse.com, rppt@kernel.org, ryan.roberts@arm.com, shuah@kernel.org, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, usama.anjum@arm.com, agordeev@linux.ibm.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, jannh@google.com, willy@infradead.org, pfalcato@suse.de, rostedt@goodmis.org, mhiramat@kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [RFC PATCH 00/57] mm/collapse: rebuild collapse on migration primitives Message-ID: References: <20260816224609.308019-1-kirill@shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: q77p4xpdff8i7dp7odzbm1nz5xmofdit X-Rspamd-Queue-Id: A535C100008 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1786961234-6482 X-HE-Meta: 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 t0Kt+zLP 8PjDDWgpSm723Tovrgg2y89WS8jpHJegIjBo/7s2Ey+9MFXoGKBbQa854j9FExR3dkT3QBNGlvlIe/VGYgvWrOkasTB8Km2yc+Dsk+Yl5GxmwgkEVaUHcOlX75mXCY6IXEz8qv18nvcdrRvfNw6MI8oOI9Se0y+kf7ZyHMGo1KjrTf1LTZgiAqv9jPf3CAEwiHAYgcUFt2fDNQ4WVimyXJJgVqVXZprNbo2+Qv9H3+AYWOunI/D3bTlG26foeAGpSZ61ikw+3E7/dbC8bfJ9aJEPU+omODhX8VXVF++V8Ru7LXDDdRqZ7Dy6C9cAHT7ble1rkFL8mVafWEIXqf8nGMkGqXm+AW0hEcEal8cKGq7MV/hn7w5mLq4aOYzCOq9poq0AhQfN9YlpGiLquDHf8Npy+64hh4EygQCTaxuAF2/yEt2PqKqouyHsjRw0RxyWIxUrk Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Aug 16, 2026 at 10:02:53PM -0400, Zi Yan wrote: > > What that removes from every collapse path: > > > > mmap_write_lock -> mmap_read > > anon_vma_lock_write() -> nothing: an rmap walk needs the folio > > locked, and the engine holds that lock > > from freeze to putback > > tlb_remove_table_sync_one() -> nothing: one ranged flush per round > > LRU isolation -> nothing: sources are inert in place > > I remember we were discussing using migration entry and the issue with > mmap_write_lock() in the context of in-place THP promotion and the > conclusion was that because MADV_DONTNEED (maybe MADV_REMOVE or > MADV_PAGEOUT) works on page table and does not change VMAs, > mmap_write_lock() is needed to prevent things being changed under > khugepaged. Anything different in normal khugepaged collapse process, so > that it is OK to use mmap_read_lock? Let me know if I misremember it. IIRC that discussion predates Hugh's pte_offset_map() rework -- since 0d940a9b270b the helper takes rcu_read_lock() and fails if the pmd is none, !present or huge, so mmap_write is no longer what keeps a pte walker out. MADV_DONTNEED is still not excluded, and the engine does not try to: the install re-reads every slot under the ptl and publishes only if it still holds the migration entry this round put there, leaving a zapped slot alone and dropping the rmap the frozen source still held. -- Kiryl Shutsemau / Kirill A. Shutemov