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 219D8C433E0 for ; Mon, 25 Jan 2021 11:18:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7F833227BF for ; Mon, 25 Jan 2021 11:18:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F833227BF 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 E78028D0002; Mon, 25 Jan 2021 06:18:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E4E788D0001; Mon, 25 Jan 2021 06:18:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D679F8D0002; Mon, 25 Jan 2021 06:18:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id BE5F88D0001 for ; Mon, 25 Jan 2021 06:18:21 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 71B683630 for ; Mon, 25 Jan 2021 11:18:21 +0000 (UTC) X-FDA: 77744048802.16.level22_481178227585 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id 44D64100E6903 for ; Mon, 25 Jan 2021 11:18:21 +0000 (UTC) X-HE-Tag: level22_481178227585 X-Filterd-Recvd-Size: 2205 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Mon, 25 Jan 2021 11:18:20 +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 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) 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 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