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 X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DBA40C5519F for ; Sun, 22 Nov 2020 13:31:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9675120760 for ; Sun, 22 Nov 2020 13:31:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="FApQXX5y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727807AbgKVNap (ORCPT ); Sun, 22 Nov 2020 08:30:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:50892 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726436AbgKVNao (ORCPT ); Sun, 22 Nov 2020 08:30:44 -0500 Received: from kernel.org (unknown [77.125.7.142]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1F44620738; Sun, 22 Nov 2020 13:30:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1606051844; bh=Ui9+fAg9vTpjZ7mDJtx+D82PTfYwHRUF4Gto5x3fYIQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FApQXX5yCoQF7ilrazML+580A6EUDC0weaeM0D0xuzwM71B3h40mSZdgpcJumUEak MUrEAso1A8L+Rp9SbsM6Ips8fCa3p7bncJcSxsSPyreo6u9/JJyTRBcJnDmbUVqjYH kVSb9u2pp0auWa98VBPxELsK19/KxaMUP2sPsXDE= Date: Sun, 22 Nov 2020 15:30:30 +0200 From: Mike Rapoport To: David Hildenbrand Cc: Michal Hocko , Muchun Song , corbet@lwn.net, mike.kravetz@oracle.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, paulmck@kernel.org, mchehab+huawei@kernel.org, pawan.kumar.gupta@linux.intel.com, rdunlap@infradead.org, oneukum@suse.com, anshuman.khandual@arm.com, jroedel@suse.de, almasrymina@google.com, rientjes@google.com, willy@infradead.org, osalvador@suse.de, song.bao.hua@hisilicon.com, duanxiongchun@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v5 21/21] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two Message-ID: <20201122133030.GG8537@kernel.org> References: <20201120064325.34492-1-songmuchun@bytedance.com> <20201120064325.34492-22-songmuchun@bytedance.com> <20201120082552.GI3200@dhcp22.suse.cz> <9b26c749-3bb6-4b16-d1fc-da7ec5d1e8a5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b26c749-3bb6-4b16-d1fc-da7ec5d1e8a5@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 20, 2020 at 10:15:30AM +0100, David Hildenbrand wrote: > On 20.11.20 09:25, Michal Hocko wrote: > > On Fri 20-11-20 14:43:25, Muchun Song wrote: > > > We only can free the unused vmemmap to the buddy system when the > > > size of struct page is a power of two. > > > > Can we actually have !power_of_2 struct pages? > > AFAIK multiples of 8 bytes (56, 64, 72) are possible. Or multiples of 4 for 32-bit (28, 32, 36). > -- > Thanks, > > David / dhildenb > > -- Sincerely yours, Mike.