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Commit 6afcf8ef authored by Ming Ling's avatar Ming Ling Committed by Linus Torvalds
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mm, compaction: fix NR_ISOLATED_* stats for pfn based migration 

Since commit bda807d4 ("mm: migrate: support non-lru movable page
migration") isolate_migratepages_block) can isolate !PageLRU pages which
would acct_isolated account as NR_ISOLATED_*.  Accounting these non-lru
pages NR_ISOLATED_{ANON,FILE} doesn't make any sense and it can misguide
heuristics based on those counters such as pgdat_reclaimable_pages resp.
too_many_isolated which would lead to unexpected stalls during the
direct reclaim without any good reason.  Note that
__alloc_contig_migrate_range can isolate a lot of pages at once.

On mobile devices such as 512M ram android Phone, it may use a big zram
swap.  In some cases zram(zsmalloc) uses too many non-lru but
migratedable pages, such as:

      MemTotal: 468148 kB
      Normal free:5620kB
      Free swap:4736kB
      Total swap:409596kB
      ZRAM: 164616kB(zsmalloc non-lru pages)
      active_anon:60700kB
      inactive_anon:60744kB
      active_file:34420kB
      inactive_file:37532kB

Fix this by only accounting lru pages to NR_ISOLATED_* in
isolate_migratepages_block right after they were isolated and we still
know they were on LRU.  Drop acct_isolated because it is called after
the fact and we've lost that information.  Batching per-cpu counter
doesn't make much improvement anyway.  Also make sure that we uncharge
only LRU pages when putting them back on the LRU in
putback_movable_pages resp.  when unmap_and_move migrates the page.

[mhocko@suse.com: replace acct_isolated() with direct counting]
Fixes: bda807d4 ("mm: migrate: support non-lru movable page migration")
Link: http://lkml.kernel.org/r/20161019080240.9682-1-mhocko@kernel.org


Signed-off-by: default avatarMing Ling <ming.ling@spreadtrum.com>
Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6d840958

mm/compaction.c

+3 −22
Original line number Diff line number Diff line
@@ -634,22 +634,6 @@ isolate_freepages_range(struct compact_control *cc, 
	return pfn;

}



/* Update the number of anon and file isolated pages in the zone */

static void acct_isolated(struct zone *zone, struct compact_control *cc)

{

	struct page *page;

	unsigned int count[2] = { 0, };



	if (list_empty(&cc->migratepages))

		return;



	list_for_each_entry(page, &cc->migratepages, lru)

		count[!!page_is_file_cache(page)]++;



	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, count[0]);

	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, count[1]);

}



/* Similar to reclaim, but different enough that they don't share logic */

static bool too_many_isolated(struct zone *zone)

{
@@ -866,6 +850,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 


		/* 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));



isolate_success:

		list_add(&page->lru, &cc->migratepages);
@@ -902,7 +888,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 
				spin_unlock_irqrestore(zone_lru_lock(zone), flags);

				locked = false;

			}

			acct_isolated(zone, cc);

			putback_movable_pages(&cc->migratepages);

			cc->nr_migratepages = 0;

			cc->last_migrated_pfn = 0;
@@ -988,7 +973,6 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, 
		if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)

			break;

	}

	acct_isolated(cc->zone, cc);



	return pfn;

}
@@ -1258,10 +1242,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, 
		low_pfn = isolate_migratepages_block(cc, low_pfn,

						block_end_pfn, isolate_mode);



		if (!low_pfn || cc->contended) {

			acct_isolated(zone, cc);

		if (!low_pfn || cc->contended)

			return ISOLATE_ABORT;

		}



		/*

		 * Either we isolated something and proceed with migration. Or
@@ -1271,7 +1253,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone, 
		break;

	}



	acct_isolated(zone, cc);

	/* Record where migration scanner will be restarted. */

	cc->migrate_pfn = low_pfn;

mm/migrate.c

+11 −4
Original line number Diff line number Diff line
@@ -168,8 +168,6 @@ void putback_movable_pages(struct list_head *l) 
			continue;

		}

		list_del(&page->lru);

		dec_node_page_state(page, NR_ISOLATED_ANON +

				page_is_file_cache(page));

		/*

		 * We isolated non-lru movable page so here we can use

		 * __PageMovable because LRU page's mapping cannot have
@@ -186,6 +184,8 @@ void putback_movable_pages(struct list_head *l) 
			put_page(page);

		} else {

			putback_lru_page(page);

			dec_node_page_state(page, NR_ISOLATED_ANON +

					page_is_file_cache(page));

		}

	}

}
@@ -1121,6 +1121,13 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, 
		 * restored.

		 */

		list_del(&page->lru);



		/*

		 * Compaction can migrate also non-LRU pages which are

		 * not accounted to NR_ISOLATED_*. They can be recognized

		 * as __PageMovable

		 */

		if (likely(!__PageMovable(page)))

			dec_node_page_state(page, NR_ISOLATED_ANON +

					page_is_file_cache(page));

	}