From: Joonsoo Kim <firstname.lastname@example.org> To: Vlastimil Babka <email@example.com> Cc: Michal Hocko <firstname.lastname@example.org>, email@example.com, Michael Ellerman <firstname.lastname@example.org>, Andrew Morton <email@example.com>, KAMEZAWA Hiroyuki <firstname.lastname@example.org>, Reza Arbab <email@example.com>, Yasuaki Ishimatsu <firstname.lastname@example.org>, email@example.com, Igor Mammedov <firstname.lastname@example.org>, Vitaly Kuznetsov <email@example.com>, LKML <firstname.lastname@example.org> Subject: Re: [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Date: Thu, 26 Oct 2017 11:47:07 +0900 Message-ID: <20171026024707.GA11791@js1304-P5Q-DELUXE> (raw) In-Reply-To: <email@example.com> On Tue, Oct 24, 2017 at 10:12:58AM +0200, Vlastimil Babka wrote: > On 10/24/2017 06:44 AM, Joonsoo Kim wrote: > >>> I'm not sure what is the confusing semantic you mentioned. I think > >>> that set_migratetype_isolate() has confusing semantic and should be > >>> fixed since making the pageblock isolated doesn't need to check if > >>> there is unmovable page or not. Do you think that > >>> set_migratetype_isolate() need to check it? If so, why? > >> > >> My intuitive understanding of set_migratetype_isolate is that it either > >> suceeds and that means that the given pfn range can be isolated for the > >> given type of allocation (be it movable or cma). No new pages will be > >> allocated from this range to allow converging into a free range in a > >> finit amount of time. At least this is how the hotplug code would like > >> to use it and I suppose that the alloc_contig_range would like to > >> guarantee the same to not rely on a fixed amount of migration attempts. > > > > Yes, alloc_contig_range() also want to guarantee the similar thing. > > Major difference between them is 'given pfn range'. memory hotplug > > works by pageblock unit but alloc_contig_range() doesn't. > > alloc_contig_range() works by the page unit. However, there is no easy > > way to isolate individual page so it uses pageblock isolation > > regardless of 'given pfn range'. In this case, checking movability of > > all pages on the pageblock would cause the problem as I mentioned > > before. > > I couldn't look too closely yet, but do I understand correctly that the > *potential* problem (because as you say there are no such > alloc_contig_range callers) you are describing is not newly introduced > by Michal's series? Then his patch fixing the introduced regression This potential problem exists there before Michal's series if the migratetype of the target pageblock isn't MIGRATE_MOVABLE or MIGRATE_CMA. However, his series enlarges this potential problem surface. It would be the problem now even if the migratetype of the target pageblock is MIGRATE_MOVABLE. > should be enough for now, and further improvements could be posted on > top, and not vice versa? Please don't take it wrong, I agree the current > state is a bit of a mess and improvements are welcome. Also it seems to I'm not very sensitive that which patch is applied first. I can do rebase. But, IMHO, correct applying order is my patch first and then Michal's series. Anyway, Michal, feel free to do what you think correct. > me that Michal is right, and there's nothing preventing > alloc_contig_range() to allocate from CMA pageblocks for non-CMA > purposes (likely not movable), and that should be also fixed? I noticed the problem you mentioned now and, yes, it should be fixed. My patch will naturally fixes this issue, too. Thanks.
next prev parent reply index Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-09-18 7:08 [PATCH v2 0/2] mm, memory_hotplug: redefine memory offline retry logic Michal Hocko 2017-09-18 7:08 ` [PATCH 1/2] mm, memory_hotplug: do not fail offlining too early Michal Hocko 2017-10-10 12:05 ` Michael Ellerman 2017-10-10 12:27 ` Michal Hocko 2017-10-11 2:37 ` Michael Ellerman 2017-10-11 5:19 ` Michael Ellerman 2017-10-11 14:05 ` Anshuman Khandual 2017-10-11 14:16 ` Michal Hocko 2017-10-11 6:51 ` Michal Hocko 2017-10-11 8:04 ` Vlastimil Babka 2017-10-11 8:13 ` Michal Hocko 2017-10-11 11:17 ` Vlastimil Babka 2017-10-11 11:24 ` Michal Hocko 2017-10-13 11:42 ` Michael Ellerman 2017-10-13 11:58 ` Michal Hocko 2017-10-13 12:00 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michal Hocko 2017-10-13 12:00 ` [PATCH 2/2] mm, page_alloc: fail has_unmovable_pages when seeing reserved pages Michal Hocko 2017-10-13 12:04 ` Vlastimil Babka 2017-10-13 12:07 ` Michal Hocko 2017-10-17 13:03 ` Vlastimil Babka 2017-10-17 11:41 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Michael Ellerman 2017-10-17 12:03 ` Michal Hocko 2017-10-17 13:02 ` Vlastimil Babka 2017-10-19 2:51 ` Joonsoo Kim 2017-10-19 7:15 ` Michal Hocko 2017-10-19 7:33 ` Joonsoo Kim 2017-10-19 8:20 ` Michal Hocko 2017-10-19 12:21 ` Michal Hocko 2017-10-20 2:13 ` Joonsoo Kim 2017-10-20 5:59 ` Michal Hocko 2017-10-20 6:50 ` Joonsoo Kim 2017-10-20 7:02 ` Michal Hocko 2017-10-23 5:23 ` Joonsoo Kim 2017-10-23 8:10 ` Michal Hocko 2017-10-24 4:44 ` Joonsoo Kim 2017-10-24 7:44 ` Michal Hocko 2017-10-24 8:12 ` Vlastimil Babka 2017-10-24 12:25 ` Michal Hocko 2017-10-26 2:47 ` Joonsoo Kim [this message] 2017-10-26 7:41 ` Michal Hocko 2017-10-20 7:22 ` Xishi Qiu 2017-10-20 8:17 ` Michal Hocko 2017-10-23 5:26 ` Joonsoo Kim 2017-10-26 13:04 ` Vlastimil Babka 2017-10-26 13:59 ` Michal Hocko 2017-09-18 7:08 ` [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline_memory Michal Hocko [not found] <AM3PR04MB14892A9D6D2FBCE21B8C1F0FF12B0@AM3PR04MB1489.eurprd04.prod.outlook.com> 2017-11-13 7:33 ` [PATCH 1/2] mm: drop migrate type checks from has_unmovable_pages Ran Wang 2017-11-13 11:02 ` Michal Hocko 2017-11-14 6:10 ` Ran Wang 2017-11-14 7:06 ` Michal Hocko 2017-11-14 7:45 ` Ran Wang
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