Messages in this thread | | | Subject | Re: [PATCH] mm/compaction: count pages and stop correctly during page isolation. | From | Vlastimil Babka <> | Date | Fri, 30 Oct 2020 15:55:45 +0100 |
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On 10/30/20 3:49 PM, Michal Hocko wrote: > On Fri 30-10-20 10:35:43, Zi Yan wrote: >> On 30 Oct 2020, at 9:36, Michal Hocko wrote: >> >> > On Fri 30-10-20 08:20:50, Zi Yan wrote: >> >> On 30 Oct 2020, at 5:43, Michal Hocko wrote: >> >> >> >>> [Cc Vlastimil] >> >>> >> >>> On Thu 29-10-20 16:04:35, Zi Yan wrote: >> >>> >> >>> Does thp_nr_pages work for __PageMovable pages? >> >> >> >> Yes. It is the same as compound_nr() but compiled >> >> to 1 when THP is not enabled. >> > >> > I am sorry but I do not follow. First of all the implementation of the >> > two is different and also I was asking about __PageMovable which should >> > never be THP IIRC. Can they be compound though? >> >> __PageMovable, non-lru movable pages, can be compound and thp_nr_page cannot >> be used for it, since when THP is off, thp_nr_page will return the wrong number. >> I got confused by its name, sorry. > > OK, this matches my understanding. Good we are on the same page. > >> But __PageMovable is irrelevant to this patch, since we are using >> __isolate_lru_page to isolate pages. non-lru __PageMovable should not appear >> after isolate_succes. thp_nr_pages can be used here. > > But this is still not clear to me. __PageMovable pages are isolated by > isolate_movable_page and then jump to isolate_succes. Does that somehow > changes the nature of the page being compound or tat thp_nr_page would > start working on those pages.
Agreed that page movable can appear after isolate_success. compound_nr() should work for both. Note that too_many_isolated() doesn't see __PageMovable isolated pages, as they are not counted as NR_ISOLATED_FILE/NR_ISOLATED_ANON, AFAIK. So in that sense they are irrelevant to the bug at hand... for now.
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