From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) (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 5CA37483806 for ; Tue, 1 Sep 2026 17:14:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=172.105.4.254 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788282883; cv=none; b=RClcqFmND4Urlahn9CAFQM10ZkB4FkjTJ/IeiDLhNPHx0Ss3a1VmOTQToidexK8E+jqavk+XtQT5Tb89WXts7NrstfVFAIgAbQL/kCXA0GSXmGK9SNk7b55QGjVskxOJ9Y6UrqYDvpOkU9+wgsaMxFUHAGtiL2v83QbaFtpsGdQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788282883; c=relaxed/simple; bh=OGFb2qA3B+EORDiZjd3N4e7IHZOF+p92KhhsxoTYZ9o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=diElZpEHxOloyRNaybRlt1MqvfPjY/6+yXGZMrj2xj0Rqb3CP5e5KbJp3wWvrB+f9EaJ7nWPh9bgCG74BKzBcsI82pVt0hG3/Wq3abGl9+3GYYTbHzu3h5rbHEFzLQIVq6MjxPO9tL60PeS54ZnoZgBSKkbwmf/aL4uiyyOPwHY= 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=WyGc8XSV; arc=none smtp.client-ip=172.105.4.254 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="WyGc8XSV" 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> 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 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