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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 8536CC4646D for ; Wed, 8 Aug 2018 07:45:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CB57216FB for ; Wed, 8 Aug 2018 07:45:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CB57216FB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727121AbeHHKEJ (ORCPT ); Wed, 8 Aug 2018 06:04:09 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45934 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726905AbeHHKEI (ORCPT ); Wed, 8 Aug 2018 06:04:08 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6537640216E8; Wed, 8 Aug 2018 07:45:40 +0000 (UTC) Received: from [10.36.117.71] (ovpn-117-71.ams2.redhat.com [10.36.117.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 23F182026DE8; Wed, 8 Aug 2018 07:45:38 +0000 (UTC) Subject: Re: [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and move it to offline_pages To: Oscar Salvador , Jerome Glisse Cc: akpm@linux-foundation.org, mhocko@suse.com, dan.j.williams@intel.com, pasha.tatashin@oracle.com, yasu.isimatu@gmail.com, logang@deltatee.com, dave.jiang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador References: <20180807133757.18352-1-osalvador@techadventures.net> <20180807133757.18352-3-osalvador@techadventures.net> <20180807135221.GA3301@redhat.com> <20180807204834.GA6844@techadventures.net> <20180807221345.GD3301@redhat.com> <20180808073835.GA9568@techadventures.net> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180808073835.GA9568@techadventures.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 08 Aug 2018 07:45:40 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 08 Aug 2018 07:45:40 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'david@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.08.2018 09:38, Oscar Salvador wrote: > On Tue, Aug 07, 2018 at 06:13:45PM -0400, Jerome Glisse wrote: >>> And since we know for sure that memhotplug-code cannot call it with ZONE_DEVICE, >>> I think this can be done easily. >> >> This might change down road but for now this is correct. They are >> talks to enumerate device memory through standard platform mechanisms >> and thus the kernel might see new types of resources down the road and >> maybe we will want to hotplug them directly from regular hotplug path >> as ZONE_DEVICE (lot of hypothetical at this point ;)). > > Well, I think that if that happens this whole thing will become > much easier, since we will not have several paths for doing the same thing. > > Another thing that I realized is that while we want to move all operation-pages > from remove_memory() path to offline_pages(), this can get tricky. > > Unless I am missing something, the devices from HMM and devm are not being registered > against "memory_subsys" struct, and so, they never get to call memory_subsys_offline() > and so offline_pages(). > > Which means that we would have to call __remove_zone() from those paths. > But this alone will not work. I mean, they move it to the zone ("replacing online/offlining code"), so they should take of removing it again. > > find_smallest/biggest_section_pfn are two functions that are being called from > > shrink_pgdat_span > and > shrink_zone_span > > to adjust zone_first_pfn/node_first_pfn and the spanned pages. > > Currently, find_smallest/biggest_section_pfn checks for the secion to be valid, > and this is fine since we are removing those sections from the remove_memory path. > > But if we want to move __remove_zone() to offline_pages(), we have to use > online_section() instead of valid_section(). > > This is all fine from offline_pages because the sections get offlined in: > > __offline_pages > offline_isolated_pages > offline_isolated_pages_cb > __offline_isolated_pages > offline_mem_sections > > > But this does not happen in HMM/devm path. > > I am pretty sure this is a dumb question, but why HMM/devm path > do not call online_pages/offline_pages? > > Thanks > -- Thanks, David / dhildenb