From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8FB28345EB1 for ; Tue, 1 Sep 2026 17:12:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=172.234.252.31 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788282743; cv=none; b=nTWVBJQAx6L5pK00Gwm/NHIL5cdwoq2qBnjHnYt6pyDbmUeGbyRCJ1eNU4v/+1HFJE8jIK+wCtOvKyrzjoLk/NPnpt8df0RH3CB7QvhE+5ep8wLYWgmQjxTMl2SguE+2QsLRYqPFvQJ88d29xYcKH7ydfGe030itCGp98pUm5Wk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788282743; c=relaxed/simple; bh=GJjpEYktLXQfUdDya8N4c9YCXPfJKcNIiYclRIysixU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aNkbTATF6frjSDu55UPqeCGxPzXpf9XrpXN4bVLiONpzLjXIt0A/U214TeS5SjMX854Ta5ns5vK24ZmnDkAElR7mkm0vaorS/SqH7JAyY+m5Rng09TYWPYgbpsHDodFe76ZdpEgQNpVvKzsbyt8ZmMFtT7qc0t1MoKcl6lh3Rrs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; spf=pass smtp.mailfrom=kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AGFJkbrl; arc=none smtp.client-ip=172.234.252.31 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AGFJkbrl" Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id D67204173D; Tue, 1 Sep 2026 17:12:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58EFC1F00A3D; Tue, 1 Sep 2026 17:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788282741; bh=StaeALLek35hMlcSHa6BZyUhT0ljTsLx6yTS5xCyYM0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=AGFJkbrleqRQzyFStbTqjNA9soKh7i/3HJhaA5YivyKFH6Le7DK3xN3u70X/XVjoy HWh5zfY3QCq0/GiCMASHtiGecXSJB+C/RfUq4r8bi/ium72Sxmxkh29JszYDD394+v uM32X/N2LJlZn2MY42zNkd2bQSsPb5sqGKGY9tAZD/qIjuPiXfhHLmXqn6U0YsxQZh WyelfqLXGVUCKno2/e+KhsojiikSyz+ONTnhJU4nqlED1LQLXmQMLudPbYWT4VwlnN 4rS+n+oW2lzrzHlfY2ulaVzUqVW8fZ8oTGFb9jZ+jxf/KJTrME3YWylmQZiyy+TXXv s1Sr457SjLhnQ== Received: from phl-compute-01.internal (phl-compute-01.internal [10.202.2.41]) by mailfauth.ams.internal (Postfix) with ESMTP id 509151980082; Tue, 1 Sep 2026 13:12:02 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-01.internal (MEProxy); Tue, 01 Sep 2026 13:12:17 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTE95wHRzu4Jku/uqR1uWajKbrR5zJX2cXnYtALksDxTaOWWCUqT0ALShYzFchhR19 jABbL3NMpQdq2Q4yk1wxABfpkhz1tXbwJ0ETPbBKtnkrOsetjBDE6HJPSHCSzQ+lV8p7hR m8B5tw0NCYc8nr5KG+JJnI7EqrKbJ9j/iB4uBQ8v3yh2BnmhuMnsKxLkWZCbcUsikaiaIb afOgG11+NHa8fIFfGiaQPV11ZUcZ/PxqcPGfORQq/nrNuM+iA2OtyKWdZtMIzuN7Y+Bitk xOhO/HMBDeF+31R8MKrPNSYAO9QueQgK/MZ6ZozJxRSVjUBLpeca5t06PFY2rHErDLj+iW 2yn2As7fL8DmU2YIyhDqY4qqwa2/ZrsmjL2YjjyNf5Ut5V+o1Q2jHYwdnRpVE4qQekDIlA 0QFGDvxUI/D1PW8k3h1xG2sm2CMe+07Xc1+6x36TyY7o9SD12A1XaguCEJgvlOl/E4/LPo GFNx+zoYsO4VdClgp1h7hc4suTeM5K0X91cofeEj76CiP8ubXYR9unXAMBRmzaTibsCFRl htnRbe1HGqYqK8cW0PalkL3qgmd3CH6stsr7YLE6PHlCrh2N2VCi400sm4iXeFTUQOgmsx q+kN/77vj/DcD2YNv53dz8Mkn5XTiexA6E9lSNNFtklTEqyElGj/pD/1naEQ X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 1 Sep 2026 13:11:59 -0400 (EDT) Date: Tue, 1 Sep 2026 18:11:57 +0100 From: Kiryl Shutsemau To: "Lorenzo Stoakes (ARM)" 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> Precedence: bulk X-Mailing-List: linux-m68k@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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. -- Kiryl Shutsemau / Kirill A. Shutemov