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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8C9A3C61DD3 for ; Tue, 1 Sep 2026 17:14:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=1PNkp7ez9jErakiPQKOI7B9sFRUtxTNZU0kcpf3jJWc=; b=Tu6orotAjW/VANmtghf+61Y/HX AbqTK/8s6HCkYjPQKbz4cRYNXcObMoM+tDG/0EWdwXHVtoR6tMbF/Hmw9kLMz5jGZm8z3067Oulfp 7JYr5OuR8WLA9D2iooZeKh36idroTczFisldg3KGb9oPvt0n8nz8rtI5Zfbt+rv0f8VJ8pNzOpK7m EJ0QUCkxkVaGk+4imOSpIAenXpCaN3nrpJzFQWtm0zeOMGO3bnad1TytmC3mv8UmLtqa5pvQ26Kgz KaBCSkpZQrkCyC0e/aFIF639yhhGi8RLnq6FetF9NuxIlPBG4A59PIJTPsLv6Z71Mzizww0XPfyLh xf6c9dSw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1S4L-0000000Cmos-0uyK; Tue, 01 Sep 2026 17:14:45 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x1S4H-0000000CmnU-3a69; Tue, 01 Sep 2026 17:14:41 +0000 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-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org 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