On Fri, Oct 30, 2020 at 11:39 AM Zi Yan <ziy@xxxxxxxxxx> wrote: > > On 30 Oct 2020, at 14:33, Yang Shi wrote: > > > On Fri, Oct 30, 2020 at 6:36 AM Michal Hocko <mhocko@xxxxxxxx> 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: > >>>>> From: Zi Yan <ziy@xxxxxxxxxx> > >>>>> > >>>>> In isolate_migratepages_block, when cc->alloc_contig is true, we are > >>>>> able to isolate compound pages, nr_migratepages and nr_isolated did not > >>>>> count compound pages correctly, causing us to isolate more pages than we > >>>>> thought. Use thp_nr_pages to count pages. Otherwise, we might be trapped > >>>>> in too_many_isolated while loop, since the actual isolated pages can go > >>>>> up to COMPACT_CLUSTER_MAX*512=16384, where COMPACT_CLUSTER_MAX is 32, > >>>>> since we stop isolation after cc->nr_migratepages reaches to > >>>>> COMPACT_CLUSTER_MAX. > >>>>> > >>>>> In addition, after we fix the issue above, cc->nr_migratepages could > >>>>> never be equal to COMPACT_CLUSTER_MAX if compound pages are isolated, > >>>>> thus page isolation could not stop as we intended. Change the isolation > >>>>> stop condition to >=. > >>>>> > >>>>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> > >>>>> --- > >>>>> mm/compaction.c | 8 ++++---- > >>>>> 1 file changed, 4 insertions(+), 4 deletions(-) > >>>>> > >>>>> diff --git a/mm/compaction.c b/mm/compaction.c > >>>>> index ee1f8439369e..0683a4999581 100644 > >>>>> --- a/mm/compaction.c > >>>>> +++ b/mm/compaction.c > >>>>> @@ -1012,8 +1012,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, > >>>>> > >>>>> isolate_success: > >>>>> list_add(&page->lru, &cc->migratepages); > >>>>> - cc->nr_migratepages++; > >>>>> - nr_isolated++; > >>>>> + cc->nr_migratepages += thp_nr_pages(page); > >>>>> + nr_isolated += thp_nr_pages(page); > >>>> > >>>> 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? > > > > I have the same question, can they be compound? If they can be > > compound, PageTransHuge() can't tell from THP and compound movable > > page, right? > > Right. I have updated the patch and use compound_nr instead. Thanks. Actually I'm wondering what kind of movable page could be compound. Any real examples? > > — > Best Regards, > Yan Zi
