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 D8181C433DB for ; Tue, 26 Jan 2021 20:14:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8DE1322255 for ; Tue, 26 Jan 2021 20:14:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732533AbhAZFY1 (ORCPT ); Tue, 26 Jan 2021 00:24:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:55492 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727657AbhAYMKV (ORCPT ); Mon, 25 Jan 2021 07:10:21 -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 B8AA2ACF4; Mon, 25 Jan 2021 12:08:36 +0000 (UTC) Date: Mon, 25 Jan 2021 13:08:32 +0100 From: Oscar Salvador To: David Hildenbrand Cc: 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, mhocko@suse.com, song.bao.hua@hisilicon.com, naoya.horiguchi@nec.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 v13 09/12] mm: hugetlb: add a kernel parameter hugetlb_free_vmemmap Message-ID: <20210125120827.GA29289@linux> References: <20210117151053.24600-1-songmuchun@bytedance.com> <20210117151053.24600-10-songmuchun@bytedance.com> <7550ebba-fdb5-0dc9-a517-dda56bd105d9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7550ebba-fdb5-0dc9-a517-dda56bd105d9@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 25, 2021 at 12:43:23PM +0100, David Hildenbrand wrote: > > - if (end - start < PAGES_PER_SECTION * sizeof(struct page)) > > + if (is_hugetlb_free_vmemmap_enabled() || > > + end - start < PAGES_PER_SECTION * sizeof(struct page)) > > This looks irresponsible. You ignore any altmap, even though current > altmap users (ZONE_DEVICE) will not actually result in applicable > vmemmaps that huge pages could ever use. > > Why do you ignore the altmap completely? This has to be properly > documented, but IMHO it's not even the right approach to mess with > altmap here. The goal was not to ignore altmap but to disable PMD mapping sections when the feature was enabled. Shame on me I did not notice that with this, altmap will be ignored. Something like below maybe: int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, struct vmem_altmap *altmap) { int err; bool populate_base_pages = false; if ((end - start < PAGES_PER_SECTION * sizeof(struct page)) || (is_hugetlb_free_vmemmap_enabled() && !altmap)) populate_base_pages = true; if (populate_base_pages) { err = vmemmap_populate_basepages(start, end, node, NULL); } else if (boot_cpu_has(X86_FEATURE_PSE)) { .... > > -- > Thanks, > > David / dhildenb > > -- Oscar Salvador SUSE L3