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 133CEC433E0 for ; Tue, 26 Jan 2021 02:56:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C1980230FA for ; Tue, 26 Jan 2021 02:56:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728847AbhAYNrx (ORCPT ); Mon, 25 Jan 2021 08:47:53 -0500 Received: from mx2.suse.de ([195.135.220.15]:43746 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729055AbhAYNoT (ORCPT ); Mon, 25 Jan 2021 08:44:19 -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 6EA6EB99F; Mon, 25 Jan 2021 11:18:19 +0000 (UTC) Date: Mon, 25 Jan 2021 12:18:17 +0100 From: Oscar Salvador To: David Hildenbrand Cc: Anshuman Khandual , akpm@linux-foundation.org, mhocko@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, vbabka@suse.cz, pasha.tatashin@soleen.com Subject: Re: [PATCH 2/5] mm,memory_hotplug: Allocate memmap from the added memory range Message-ID: <20210125111816.GB28363@linux> References: <20201217130758.11565-1-osalvador@suse.de> <20201217130758.11565-3-osalvador@suse.de> <21079c2d-67d0-fc59-8d7f-0795b3f8a3e3@redhat.com> <20210125103951.GA27851@linux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 25, 2021 at 11:57:20AM +0100, David Hildenbrand wrote: > I'm confused. > > 1. Assume we hotplug memory, online it to ZONE_MOVABLE. The vmemmap gets > allocated from altmap space. The vmemmap could have never been allocated from altmap in case hpage vmemmap feature is enabled. Have a look at [1]. If is_hugetlb_free_vmemmap_enabled(), vmemmap_populate() ends up calling vmemmap_populate_basepages(). And since no memory was consumed from altmap, and hence altmap_alloc_block_buf() was never called, vmem_altmap->alloc will be 0, and memory_block->nr_vmemmap_pages will be 0 as well. But on a second though, true is that we will get in trouble if hpage vmemmap feature ever gets to work with vmemmap_populate_hugepages. I will queue that to look in a new future. [1] https://patchwork.kernel.org/project/linux-mm/patch/20210117151053.24600-10-songmuchun@bytedance.com/ -- Oscar Salvador SUSE L3