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. — Best Regards, Yan Zi
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