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? > > -- > Michal Hocko > SUSE Labs >
