Commit 1da2f328 authored by Rik van Riel's avatar Rik van Riel Committed by Linus Torvalds
Browse files

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@surriel.com: fix hugetlbfs pages per Mike, cleanup per Vlastimil]
  Link: http://lkml.kernel.org/r/20200228104700.0af2f18d@imladris.surriel.com


Signed-off-by: default avatarRik van Riel <riel@surriel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Link: http://lkml.kernel.org/r/20200227213238.1298752-2-riel@surriel.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b06eda09

mm/compaction.c

+13 −9
Original line number Diff line number Diff line
@@ -894,12 +894,13 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 


		/*

		 * 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 compact_control *cc, unsigned long low_pfn, 
			 * 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 compact_control *cc, unsigned long low_pfn, 
		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);

mm/page_alloc.c

+7 −2
Original line number Diff line number Diff line
@@ -8251,15 +8251,20 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, 


		/*

		 * 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 (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;

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