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? -- Michal Hocko SUSE Labs
