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=-2.3 required=3.0 tests=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 5F6AECA9EA1 for ; Fri, 18 Oct 2019 11:51:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A3AF20700 for ; Fri, 18 Oct 2019 11:51:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2633635AbfJRLvQ (ORCPT ); Fri, 18 Oct 2019 07:51:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729946AbfJRLvP (ORCPT ); Fri, 18 Oct 2019 07:51:15 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 55E59756; Fri, 18 Oct 2019 11:51:15 +0000 (UTC) Received: from [10.36.118.23] (unknown [10.36.118.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8FD1360BF4; Fri, 18 Oct 2019 11:51:13 +0000 (UTC) Subject: Re: memory offline infinite loop after soft offline To: Michal Hocko Cc: Naoya Horiguchi , Qian Cai , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Mike Kravetz References: <20191017093410.GA19973@hori.linux.bs1.fc.nec.co.jp> <20191017100106.GF24485@dhcp22.suse.cz> <1571335633.5937.69.camel@lca.pw> <20191017182759.GN24485@dhcp22.suse.cz> <20191018021906.GA24978@hori.linux.bs1.fc.nec.co.jp> <33946728-bdeb-494a-5db8-e279acebca47@redhat.com> <20191018082459.GE5017@dhcp22.suse.cz> <20191018085528.GG5017@dhcp22.suse.cz> <3ac0ad7a-7dd2-c851-858d-2986fa8d44b6@redhat.com> <20191018113437.GJ5017@dhcp22.suse.cz> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <0ee3f0d3-470b-a42f-6b4b-805dfc891b7a@redhat.com> Date: Fri, 18 Oct 2019 13:51:12 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191018113437.GJ5017@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 18 Oct 2019 11:51:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18.10.19 13:34, Michal Hocko wrote: > On Fri 18-10-19 13:00:45, David Hildenbrand wrote: >> On 18.10.19 10:55, Michal Hocko wrote: >>> On Fri 18-10-19 10:38:21, David Hildenbrand wrote: >>>> On 18.10.19 10:24, Michal Hocko wrote: >>>>> On Fri 18-10-19 10:13:36, David Hildenbrand wrote: >>>>> [...] >>>>>> However, if the compound page spans multiple pageblocks >>>>> >>>>> Although hugetlb pages spanning pageblocks are possible this shouldn't >>>>> matter in__test_page_isolated_in_pageblock because this function doesn't >>>>> really operate on pageblocks as the name suggests. It is simply >>>>> traversing all valid RAM ranges (see walk_system_ram_range). >>>> >>>> As long as the hugepages don't span memory blocks/sections, you are right. I >>>> have no experience with gigantic pages in this regard. >>> >>> They can clearly span sections (1GB is larger than 128MB). Why do you >>> think it matters actually? walk_system_ram_range walks RAM ranges and no >>> allocation should span holes in RAM right? >>> >> >> Let's explore what I was thinking. If we can agree that any compound page is >> always aligned to its size , then what I tell here is not applicable. I know >> it is true for gigantic pages. >> >> Some extreme example to clarify >> >> [ memory block 0 (128MB) ][ memory block 1 (128MB) ] >> [ compound page (128MB) ] >> >> If you would offline memory block 1, and you detect PG_offline on the first >> page of that memory block (PageHWPoison(compound_head(page))), you would >> jump over the whole memory block (pfn += 1 << compound_order(page)), leaving >> 64MB of the memory block unchecked. >> >> Again, if any compound page has the alignment restrictions (PFN of head >> aligned to 1 << compound_order(page)), this is not possible. >> >> >> If it is, however, possible, the "clean" thing would be to only jump over >> the remaining part of the compound page, e.g., something like >> >> pfn += (1 << compound_order(page)) - (page - compound_head(page))); > > OK, I see what you mean now. In other words similar to eeb0efd071d82. > Exactly. -- Thanks, David / dhildenb