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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 D382ECA9EA0 for ; Fri, 18 Oct 2019 11:34:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC27F222BD for ; Fri, 18 Oct 2019 11:34:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571398481; bh=vIUo2Tn4Of2EyGa5CUiHbSN+bVQHwxjBx5sZD5Wyi64=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ryW6/O3P/Nmh5+0FZaCRjIHAta9QgoNIIFAtAiN3NdH5mkS5x6diuYWhGnB8hMz4A bTr0te+oKStCtIJhe8IY35OSU839u3fQUN2MT/5fF33LQ6N0Z9bAIRXEfiRlhHoVo8 2jB45uwSawUJAODOp6BCeNVbu4A9n15PO1j+KnmQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404865AbfJRLek (ORCPT ); Fri, 18 Oct 2019 07:34:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:53282 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2391782AbfJRLek (ORCPT ); Fri, 18 Oct 2019 07:34:40 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 789E7AFC3; Fri, 18 Oct 2019 11:34:38 +0000 (UTC) Date: Fri, 18 Oct 2019 13:34:37 +0200 From: Michal Hocko To: David Hildenbrand Cc: Naoya Horiguchi , Qian Cai , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Mike Kravetz Subject: Re: memory offline infinite loop after soft offline Message-ID: <20191018113437.GJ5017@dhcp22.suse.cz> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ac0ad7a-7dd2-c851-858d-2986fa8d44b6@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Michal Hocko SUSE Labs