From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753649AbdCIIAw (ORCPT ); Thu, 9 Mar 2017 03:00:52 -0500 Received: from mx2.suse.de ([195.135.220.15]:37674 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752526AbdCIH67 (ORCPT ); Thu, 9 Mar 2017 02:58:59 -0500 Subject: Re: + compaction-add-def_blk_aops-migrate-function-for-memory-compaction.patch added to -mm tree To: akpm@linux-foundation.org, zhouxianrong@huawei.com, Mi.Sophia.Wang@huawei.com, hannes@cmpxchg.org, kirill.shutemov@linux.intel.com, mgorman@techsingularity.net, minchan@kernel.org, viro@zeniv.linux.org.uk, weidu.du@huawei.com, won.ho.park@huawei.com, zhangshiming5@huawei.com, zhouxiaoyan1@huawei.com, zhouxiyu@huawei.com, mm-commits@vger.kernel.org, Jan Kara , Hugh Dickins , Linux-FSDevel , LKML , "Kirill A. Shutemov" References: <58c099dc.qZs+2fQBHcULYdhi%akpm@linux-foundation.org> From: Vlastimil Babka Message-ID: <6867e5fe-b67e-fe01-4cc4-8338b4043577@suse.cz> Date: Thu, 9 Mar 2017 08:58:45 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <58c099dc.qZs+2fQBHcULYdhi%akpm@linux-foundation.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/09/2017 12:55 AM, akpm@linux-foundation.org wrote: > > The patch titled > Subject: compaction: add def_blk_aops migrate function for memory compaction > has been added to the -mm tree. Its filename is > compaction-add-def_blk_aops-migrate-function-for-memory-compaction.patch > > This patch should soon appear at > http://ozlabs.org/~akpm/mmots/broken-out/compaction-add-def_blk_aops-migrate-function-for-memory-compaction.patch > and later at > http://ozlabs.org/~akpm/mmotm/broken-out/compaction-add-def_blk_aops-migrate-function-for-memory-compaction.patch > > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/SubmitChecklist when testing your code *** > > The -mm tree is included into linux-next and is updated > there every 3-4 working days > > ------------------------------------------------------ > From: zhouxianrong > Subject: compaction: add def_blk_aops migrate function for memory compaction That's not really a mm/compaction patch, but a block layer/migration patch. I don't know internals of those so well, so I added some CC's. > The reason for doing this is based on two factors. > > 1. larg file read/write operations with order 0 can fragmentize > memory rapidly. > > 2. when a special filesystem does not supply migratepage callback, > kernel would fallback to default function fallback_migrate_page. > but fallback_migrate_page could not migrate diry page nicely; > specially kcompactd with MIGRATE_SYNC_LIGHT could not migrate > diry pages due to this until clear_page_dirty_for_io in some > procedure. i think it is not suitable here in this scenario. > for dirty pages we should migrate it rather than skip or writeout > it in kcomapctd with MIGRATE_SYNC_LIGHT. i think this problem is > for all filesystem without migratepage not only for block device fs. > > So for compaction under large file writing supply migratepage for > def_blk_aops. Is this really safe to do? buffer_migrate_page() has some assumptions listed in its comment (and maybe more that are not listed). Do we know it's safe to use it for all def_blk_aops users? > Link: http://lkml.kernel.org/r/1488937915-78955-1-git-send-email-zhouxianrong@huawei.com > Signed-off-by: zhouxianrong > Cc: Kirill A. Shutemov > Cc: Johannes Weiner > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Vlastimil Babka > Cc: Al Viro > Cc: > Cc: > Cc: > Cc: > Cc: > Cc: > Signed-off-by: Andrew Morton > --- > > fs/block_dev.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff -puN fs/block_dev.c~compaction-add-def_blk_aops-migrate-function-for-memory-compaction fs/block_dev.c > --- a/fs/block_dev.c~compaction-add-def_blk_aops-migrate-function-for-memory-compaction > +++ a/fs/block_dev.c > @@ -2064,6 +2064,9 @@ static const struct address_space_operat > .releasepage = blkdev_releasepage, > .direct_IO = blkdev_direct_IO, > .is_dirty_writeback = buffer_check_dirty_writeback, > +#ifdef CONFIG_MIGRATION > + .migratepage = buffer_migrate_page, > +#endif > }; > > #define BLKDEV_FALLOC_FL_SUPPORTED \ > _ > > Patches currently in -mm which might be from zhouxianrong@huawei.com are > > compaction-add-def_blk_aops-migrate-function-for-memory-compaction.patch >