From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbdG0L5u (ORCPT ); Thu, 27 Jul 2017 07:57:50 -0400 Received: from mx2.suse.de ([195.135.220.15]:45114 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750992AbdG0L5t (ORCPT ); Thu, 27 Jul 2017 07:57:49 -0400 Subject: Re: gigantic hugepages vs. movable zones To: Michal Hocko , "Aneesh Kumar K.V" Cc: Luiz Capitulino , Mike Kravetz , linux-mm@kvack.org, LKML , Joonsoo Kim References: <20170726105004.GI2981@dhcp22.suse.cz> <87inie1uwf.fsf@linux.vnet.ibm.com> <20170727072857.GI20970@dhcp22.suse.cz> <1529e986-5f28-35dd-c82e-a4b5801b4afd@linux.vnet.ibm.com> <20170727081236.GK20970@dhcp22.suse.cz> <20170727082258.GL20970@dhcp22.suse.cz> From: Vlastimil Babka Message-ID: Date: Thu, 27 Jul 2017 13:56:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170727082258.GL20970@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/27/2017 10:22 AM, Michal Hocko wrote: > [CC for real] > > On Thu 27-07-17 10:12:36, Michal Hocko wrote: >> On Thu 27-07-17 13:30:31, Aneesh Kumar K.V wrote: >>> >>> >>> On 07/27/2017 12:58 PM, Michal Hocko wrote: >>>> On Thu 27-07-17 07:52:08, Aneesh Kumar K.V wrote: >>>>> Michal Hocko writes: >>>>> >>>>>> Hi, >>>>>> I've just noticed that alloc_gigantic_page ignores movability of the >>>>>> gigantic page and it uses any existing zone. Considering that >>>>>> hugepage_migration_supported only supports 2MB and pgd level hugepages >>>>>> then 1GB pages are not migratable and as such allocating them from a >>>>>> movable zone will break the basic expectation of this zone. Standard >>>>>> hugetlb allocations try to avoid that by using htlb_alloc_mask and I >>>>>> believe we should do the same for gigantic pages as well. >>>>>> >>>>>> I suspect this behavior is not intentional. What do you think about the >>>>>> following untested patch? >>>>> >>>>> >>>>> I also noticed an unrelated issue with the usage of >>>>> start_isolate_page_range. On error we set the migrate type to >>>>> MIGRATE_MOVABLE. >>>> >>>> Why that should be a problem? I think it is perfectly OK to have >>>> MIGRATE_MOVABLE pageblocks inside kernel zones. >>>> >>> >>> we can pick pages with migrate type movable and if we fail to isolate won't ^ CMA >>> we set the migrate type of that pages to MOVABLE ? Yes, it seems we can silently kill CMA pageblocks in such case. Joonsoo, can you check? >> >> I do not see an immediate problem. GFP_KERNEL allocations can fallback >> to movable migrate pageblocks AFAIR. But I am not very much familiar >> with migratetypes. Vlastimil, could you have a look please? >