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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 323E1C2D0E4 for ; Tue, 24 Nov 2020 10:25:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8C43206CA for ; Tue, 24 Nov 2020 10:25:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731012AbgKXKYx (ORCPT ); Tue, 24 Nov 2020 05:24:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:45204 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727982AbgKXKYx (ORCPT ); Tue, 24 Nov 2020 05:24:53 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A3B03AC48; Tue, 24 Nov 2020 10:24:51 +0000 (UTC) Date: Tue, 24 Nov 2020 11:24:45 +0100 From: Oscar Salvador To: Muchun Song Cc: 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, mhocko@suse.com, 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 v6 07/16] x86/mm/64: Disable PMD page mapping of vmemmap Message-ID: <20201124102441.GA24718@linux> References: <20201124095259.58755-1-songmuchun@bytedance.com> <20201124095259.58755-8-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201124095259.58755-8-songmuchun@bytedance.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Nov 24, 2020 at 05:52:50PM +0800, Muchun Song wrote: > If we enable the CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, we can just > disbale PMD page mapping of vmemmap to simplify the code. In this > case, we do not need complex code doing vmemmap page table > manipulation. This is a way to simply the first version of this > patch series. In the future, we can add some code doing page table > manipulation. IIRC, CONFIG_HUGETLB_PAGE_FREE_VMEMMAP was supposed to be enabled by default, right? And we would control whether we __really__ want to this by a boot option, which was disabled by default? If you go for populating the memmap with basepages by checking CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, would not everybody, even the ones that did not enable this by the boot option be affected? -- Oscar Salvador SUSE L3