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 8C228C56202 for ; Tue, 24 Nov 2020 10:24:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D933C206CA for ; Tue, 24 Nov 2020 10:24:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D933C206CA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1A7D26B00A9; Tue, 24 Nov 2020 05:24:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1579D6B00AA; Tue, 24 Nov 2020 05:24:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 06EB66B00AB; Tue, 24 Nov 2020 05:24:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0139.hostedemail.com [216.40.44.139]) by kanga.kvack.org (Postfix) with ESMTP id E562A6B00A9 for ; Tue, 24 Nov 2020 05:24:53 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id AD93A180AD811 for ; Tue, 24 Nov 2020 10:24:53 +0000 (UTC) X-FDA: 77518928466.20.bells07_2b1321c2736d Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin20.hostedemail.com (Postfix) with ESMTP id 89965180C07AF for ; Tue, 24 Nov 2020 10:24:53 +0000 (UTC) X-HE-Tag: bells07_2b1321c2736d X-Filterd-Recvd-Size: 2453 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Tue, 24 Nov 2020 10:24:52 +0000 (UTC) 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) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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