From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934774Ab3BTJ6h (ORCPT ); Wed, 20 Feb 2013 04:58:37 -0500 Received: from mail-yh0-f45.google.com ([209.85.213.45]:47527 "EHLO mail-yh0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756797Ab3BTJ6e (ORCPT ); Wed, 20 Feb 2013 04:58:34 -0500 X-Greylist: delayed 83990 seconds by postgrey-1.27 at vger.kernel.org; Wed, 20 Feb 2013 04:58:34 EST Message-ID: <51249E3E.9070909@gmail.com> Date: Wed, 20 Feb 2013 17:58:22 +0800 From: Simon Jeons User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Mel Gorman CC: Andrew Morton , Lin Feng , bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org, walken@google.com, kamezawa.hiroyu@jp.fujitsu.com, minchan@kernel.org, riel@redhat.com, rientjes@google.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, jiang.liu@huawei.com, mhocko@suse.cz, linux-mm@kvack.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable() References: <1359972248-8722-1-git-send-email-linfeng@cn.fujitsu.com> <1359972248-8722-2-git-send-email-linfeng@cn.fujitsu.com> <20130204160624.5c20a8a0.akpm@linux-foundation.org> <20130205115722.GF21389@suse.de> <20130205133244.GH21389@suse.de> In-Reply-To: <20130205133244.GH21389@suse.de> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/05/2013 09:32 PM, Mel Gorman wrote: > On Tue, Feb 05, 2013 at 11:57:22AM +0000, Mel Gorman wrote: >>>> + migrate_pre_flag = 1; >>>> + } >>>> + >>>> + if (!isolate_lru_page(pages[i])) { >>>> + inc_zone_page_state(pages[i], NR_ISOLATED_ANON + >>>> + page_is_file_cache(pages[i])); >>>> + list_add_tail(&pages[i]->lru, &pagelist); >>>> + } else { >>>> + isolate_err = 1; >>>> + goto put_page; >>>> + } >> isolate_lru_page() takes the LRU lock every time. > Credit to Michal Hocko for bringing this up but with the number of > other issues I missed that this is also broken with respect to huge page > handling. hugetlbfs pages will not be on the LRU so the isolation will mess > up and the migration has to be handled differently. Ordinarily hugetlbfs > pages cannot be allocated from ZONE_MOVABLE but it is possible to configure > it to be allowed via /proc/sys/vm/hugepages_treat_as_movable. If this > encounters a hugetlbfs page, it'll just blow up. As you said, hugetlbfs pages are not in LRU list, then how can encounter a hugetlbfs page and blow up? > > The other is that this almost certainly broken for transhuge page > handling. gup returns the head and tail pages and ordinarily this is ok When need gup thp? in kvm case? > because the caller only cares about the physical address. Migration will > also split a hugepage if it receives it but you are potentially adding > tail pages to a list here and then migrating them. The split of the first > page will get very confused. I'm not exactly sure what the result will be > but it won't be pretty. > > Was THP enabled when this was tested? Was CONFIG_DEBUG_LIST enabled > during testing? > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Jeons Subject: Re: [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable() Date: Wed, 20 Feb 2013 17:58:22 +0800 Message-ID: <51249E3E.9070909@gmail.com> References: <1359972248-8722-1-git-send-email-linfeng@cn.fujitsu.com> <1359972248-8722-2-git-send-email-linfeng@cn.fujitsu.com> <20130204160624.5c20a8a0.akpm@linux-foundation.org> <20130205115722.GF21389@suse.de> <20130205133244.GH21389@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: Andrew Morton , Lin Feng , bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org, walken@google.com, kamezawa.hiroyu@jp.fujitsu.com, minchan@kernel.org, riel@redhat.com, rientjes@google.com, isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com, jiang.liu@huawei.com, mhocko@suse.cz, linux-mm@kvack.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Mel Gorman Return-path: In-Reply-To: <20130205133244.GH21389@suse.de> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On 02/05/2013 09:32 PM, Mel Gorman wrote: > On Tue, Feb 05, 2013 at 11:57:22AM +0000, Mel Gorman wrote: >>>> + migrate_pre_flag = 1; >>>> + } >>>> + >>>> + if (!isolate_lru_page(pages[i])) { >>>> + inc_zone_page_state(pages[i], NR_ISOLATED_ANON + >>>> + page_is_file_cache(pages[i])); >>>> + list_add_tail(&pages[i]->lru, &pagelist); >>>> + } else { >>>> + isolate_err = 1; >>>> + goto put_page; >>>> + } >> isolate_lru_page() takes the LRU lock every time. > Credit to Michal Hocko for bringing this up but with the number of > other issues I missed that this is also broken with respect to huge page > handling. hugetlbfs pages will not be on the LRU so the isolation will mess > up and the migration has to be handled differently. Ordinarily hugetlbfs > pages cannot be allocated from ZONE_MOVABLE but it is possible to configure > it to be allowed via /proc/sys/vm/hugepages_treat_as_movable. If this > encounters a hugetlbfs page, it'll just blow up. As you said, hugetlbfs pages are not in LRU list, then how can encounter a hugetlbfs page and blow up? > > The other is that this almost certainly broken for transhuge page > handling. gup returns the head and tail pages and ordinarily this is ok When need gup thp? in kvm case? > because the caller only cares about the physical address. Migration will > also split a hugepage if it receives it but you are potentially adding > tail pages to a list here and then migrating them. The split of the first > page will get very confused. I'm not exactly sure what the result will be > but it won't be pretty. > > Was THP enabled when this was tested? Was CONFIG_DEBUG_LIST enabled > during testing? > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org