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 E7078C624D3 for ; Tue, 1 Sep 2026 17:14:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EB23B6B00AD; Tue, 1 Sep 2026 13:14:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E620D6B00AE; Tue, 1 Sep 2026 13:14:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D522C6B00AF; Tue, 1 Sep 2026 13:14:43 -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 A3DFB6B00AD for ; Tue, 1 Sep 2026 13:14:43 -0400 (EDT) Received: from smtpin16.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 3C0361404AB for ; Tue, 1 Sep 2026 17:14:43 +0000 (UTC) X-FDA: 85165842846.16.CBC3200 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf28.hostedemail.com (Postfix) with ESMTP id AA63BC000B for ; Tue, 1 Sep 2026 17:14:41 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WyGc8XSV; spf=pass (imf28.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788282881; 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=1PNkp7ez9jErakiPQKOI7B9sFRUtxTNZU0kcpf3jJWc=; b=FmlMZXVpeQMes3DfiboaZn78a5YnqsAU5aHFU5duRNSN/0UP1l8zT/fIJ6qPuams4JrCDF mqqVejfrIU7quO8QL+rwkk9KqPAC5LpA3caXYnD3qUAI1LCvvJAvyj8uPVTZVZXVYE+x8D Ur5zjBIynpCwPCd5iBjTElxWRBq4w0M= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788282881; b=E0cCekIdb/DFOxS+58uYWb00279ooulRTivXcsiy1U0IWZfD6y75y7SDMtjSsGupevrNJ3 hVp/UG0oC/zvvrwN9IHlxGKS4wzd35rvrJ45KRx79bdc77A3dWvtiOWndHwtp3uqeG8sPP 0pKguJG1nBNBvzX7tnPnx3PjJBDrkns= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WyGc8XSV; spf=pass (imf28.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 481356013A; Tue, 1 Sep 2026 17:14:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 563FE1F000E9; Tue, 1 Sep 2026 17:14:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788282881; bh=1PNkp7ez9jErakiPQKOI7B9sFRUtxTNZU0kcpf3jJWc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=WyGc8XSV+h5QaC5hrytW/vJLWXzYZQZJxWveh4LcjaDsd1IWOINhAcGPiYhISOsLo OSSdCjOizMPKQZXR2T+u5d8YeyJ0w0XUMVwautKGnwupK6xSsdLd57wV979q/6rA8i 2+TkAPP7HmGk/XtHJ3EpB24En1Ix+6oYBfTNUJrEQf5D3oyrMxBXMXCYFfIwSlgEHM pSTP37qXlVGUJw0e/z1Tii9u2hm4ByGXX+kZTv428piYykVP1aDkLZkvtkl8B4vVrZ r+SRmOn2ziSMauikcMFr/wbjsF/EUiHXzzHcyMBvmKBcKGquGY/wktocgGQ6amFEia w36rT04Ny6Ffg== Date: Tue, 1 Sep 2026 18:14:08 +0100 From: "Lorenzo Stoakes (ARM)" To: Kiryl Shutsemau Cc: Jason Gunthorpe , Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Guo Ren , Brian Cain , Geert Uytterhoeven , Dinh Nguyen , Simon Schuster , Jonas Bonn , Stefan Kristiansson , Stafford Horne , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Russell King , Vineet Gupta , Michal Simek , Chris Zankel , Max Filippov , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , "David S. Miller" , Andreas Larsson , Richard Henderson , Matt Turner , Magnus Lindholm , Catalin Marinas , Mark Rutland , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Richard Weinberger , Anton Ivanov , Johannes Berg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , John Hubbard , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, linux-arch@vger.kernel.org, sparclinux@vger.kernel.org, linux-alpha@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-um@lists.infradead.org, Hugh Dickins , Qi Zheng Subject: Re: [PATCH 01/12] mm/huge_memory: zap deposited page tables after an RCU grace period Message-ID: References: <20260901-rcu-pagetable-freeing-v1-0-5456a81c8212@kernel.org> <20260901-rcu-pagetable-freeing-v1-1-5456a81c8212@kernel.org> <20260901142408.GA56830@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: gwjqc1n6jqo51eto5ghxuyu8dd3nf51p X-Rspamd-Queue-Id: AA63BC000B X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788282881-492153 X-HE-Meta: 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 HIO76UGH qnBlbySgDKhqgJXLqnYNJE5skGsjPvrGDhOf2aFcA4Yo0nIT02Cr6W6FbIfOznS1OwWTTXdE1FCPxnyeRTXeiVxCekHBj19dhpg9Cw71OXmhBO4gwOn9U5X+iJrSVZGKi0fj4DMMtdvk28esRTelI1qS5cIEW3wqn2swTbC3OlZNzJzhvttctZblj/33vLiCP5hZ9tuiA5cEefGzUxu0AV6yOxp3R0kMePEDFQ58ejkc3fbxfBWGoGlsQxIH65OOOl/HHX0ycFxn+VP0MsVkyOLw6doBCDEX2sr1wG8TirXsdtNq6Q4DmNtxpODgv1kL5w5sp4k3OmGS0JmeErzoJtyNyPvOUEhhSpxgagtpPZw2f8BtU+UOYNA8D5A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 01, 2026 at 06:11:57PM +0100, Kiryl Shutsemau wrote: > On Tue, Sep 01, 2026 at 04:45:14PM +0100, Lorenzo Stoakes (ARM) wrote: > > > munmap() of 64G worth of THP should be enough to demonstrate the > > > problem. > > > > I mean you're going to hit that from RCU freeing page tables already, which > > most architectures already do right? > > Not at the same rate -- tlb_remove_table() batches into struct > mmu_table_batch. One call_rcu() per MAX_TABLE_BATCH. > > > So if RCU saturation is a problem, that problem already exists, but I've > > not heard of that being a problem at all? > > I did quick test and I don't see a measurable difference in munmap() > wall time of 40G of THPs. I see ~17x more softirqs, but this is > expected. > > The objection is retracted. > > We can return to this later if it is going to be visible anywhere. Great thanks! :) > > -- > Kiryl Shutsemau / Kirill A. Shutemov -- Cheers, Lorenzo