From: Rik van Riel <riel@xxxxxxxxxxx> Subject: mm,thp,compaction,cma: allow THP migration for CMA allocations The code to implement THP migrations already exists, and the code for CMA to clear out a region of memory already exists. Only a few small tweaks are needed to allow CMA to move THP memory when attempting an allocation from alloc_contig_range. With these changes, migrating THPs from a CMA area works when allocating a 1GB hugepage from CMA memory. [riel@xxxxxxxxxxx: fix hugetlbfs pages per Mike, cleanup per Vlastimil] Link: http://lkml.kernel.org/r/20200228104700.0af2f18d@xxxxxxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20200227213238.1298752-2-riel@xxxxxxxxxxx Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Joonsoo Kim <js1304@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 22 +++++++++++++--------- mm/page_alloc.c | 9 +++++++-- 2 files changed, 20 insertions(+), 11 deletions(-) --- a/mm/compaction.c~mmthpcompactioncma-allow-thp-migration-for-cma-allocations +++ a/mm/compaction.c @@ -894,12 +894,13 @@ isolate_migratepages_block(struct compac /* * Regardless of being on LRU, compound pages such as THP and - * hugetlbfs are not to be compacted. We can potentially save - * a lot of iterations if we skip them at once. The check is - * racy, but we can consider only valid values and the only - * danger is skipping too much. + * hugetlbfs are not to be compacted unless we are attempting + * an allocation much larger than the huge page size (eg CMA). + * We can potentially save a lot of iterations if we skip them + * at once. The check is racy, but we can consider only valid + * values and the only danger is skipping too much. */ - if (PageCompound(page)) { + if (PageCompound(page) && !cc->alloc_contig) { const unsigned int order = compound_order(page); if (likely(order < MAX_ORDER)) @@ -969,7 +970,7 @@ isolate_migratepages_block(struct compac * and it's on LRU. It can only be a THP so the order * is safe to read and it's 0 for tail pages. */ - if (unlikely(PageCompound(page))) { + if (unlikely(PageCompound(page) && !cc->alloc_contig)) { low_pfn += compound_nr(page) - 1; goto isolate_fail; } @@ -981,12 +982,15 @@ isolate_migratepages_block(struct compac if (__isolate_lru_page(page, isolate_mode) != 0) goto isolate_fail; - VM_BUG_ON_PAGE(PageCompound(page), page); + /* The whole page is taken off the LRU; skip the tail pages. */ + if (PageCompound(page)) + low_pfn += compound_nr(page) - 1; /* Successfully isolated */ del_page_from_lru_list(page, lruvec, page_lru(page)); - inc_node_page_state(page, - NR_ISOLATED_ANON + page_is_file_cache(page)); + mod_node_page_state(page_pgdat(page), + NR_ISOLATED_ANON + page_is_file_cache(page), + hpage_nr_pages(page)); isolate_success: list_add(&page->lru, &cc->migratepages); --- a/mm/page_alloc.c~mmthpcompactioncma-allow-thp-migration-for-cma-allocations +++ a/mm/page_alloc.c @@ -8251,15 +8251,20 @@ struct page *has_unmovable_pages(struct /* * Hugepages are not in LRU lists, but they're movable. + * THPs are on the LRU, but need to be counted as #small pages. * We need not scan over tail pages because we don't * handle each tail page individually in migration. */ - if (PageHuge(page)) { + if (PageHuge(page) || PageTransCompound(page)) { struct page *head = compound_head(page); unsigned int skip_pages; - if (!hugepage_migration_supported(page_hstate(head))) + if (PageHuge(page)) { + if (!hugepage_migration_supported(page_hstate(head))) + return page; + } else if (!PageLRU(head) && !__PageMovable(head)) { return page; + } skip_pages = compound_nr(head) - (page - head); iter += skip_pages - 1; _
