Commit 060f005f authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Linus Torvalds
Browse files

mm/vmscan.c: do not allocate duplicate stack variables in shrink_page_list() 

On path shrink_inactive_list() ---> shrink_page_list() we allocate stack
variables for the statistics twice.  This is completely useless, and
this just consumes stack much more, then we really need.

The patch kills duplicate stack variables from shrink_page_list(), and
this reduce stack usage and object file size significantly:

Stack usage:
  Before: vmscan.c:1122:22:shrink_page_list	648	static
  After:  vmscan.c:1122:22:shrink_page_list	616	static

Size of vmscan.o:
           text	   data	    bss	    dec	    hex	filename
  Before: 56866	   4720	    128	  61714	   f112	mm/vmscan.o
  After:  56770	   4720	    128	  61618	   f0b2	mm/vmscan.o

Link: http://lkml.kernel.org/r/154894900030.5211.12104993874109647641.stgit@localhost.localdomain


Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: default avatarDaniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2cee57d1

mm/vmscan.c

+14 −30
Original line number Diff line number Diff line
@@ -1106,16 +1106,9 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
{

	LIST_HEAD(ret_pages);

	LIST_HEAD(free_pages);

	int pgactivate = 0;

	unsigned nr_unqueued_dirty = 0;

	unsigned nr_dirty = 0;

	unsigned nr_congested = 0;

	unsigned nr_reclaimed = 0;

	unsigned nr_writeback = 0;

	unsigned nr_immediate = 0;

	unsigned nr_ref_keep = 0;

	unsigned nr_unmap_fail = 0;



	memset(stat, 0, sizeof(*stat));

	cond_resched();



	while (!list_empty(page_list)) {
@@ -1159,10 +1152,10 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
		 */

		page_check_dirty_writeback(page, &dirty, &writeback);

		if (dirty || writeback)

			nr_dirty++;

			stat->nr_dirty++;



		if (dirty && !writeback)

			nr_unqueued_dirty++;

			stat->nr_unqueued_dirty++;



		/*

		 * Treat this page as congested if the underlying BDI is or if
@@ -1174,7 +1167,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
		if (((dirty || writeback) && mapping &&

		     inode_write_congested(mapping->host)) ||

		    (writeback && PageReclaim(page)))

			nr_congested++;

			stat->nr_congested++;



		/*

		 * If a page at the tail of the LRU is under writeback, there
@@ -1223,7 +1216,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
			if (current_is_kswapd() &&

			    PageReclaim(page) &&

			    test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {

				nr_immediate++;

				stat->nr_immediate++;

				goto activate_locked;



			/* Case 2 above */
@@ -1241,7 +1234,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
				 * and it's also appropriate in global reclaim.

				 */

				SetPageReclaim(page);

				nr_writeback++;

				stat->nr_writeback++;

				goto activate_locked;



			/* Case 3 above */
@@ -1261,7 +1254,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
		case PAGEREF_ACTIVATE:

			goto activate_locked;

		case PAGEREF_KEEP:

			nr_ref_keep++;

			stat->nr_ref_keep++;

			goto keep_locked;

		case PAGEREF_RECLAIM:

		case PAGEREF_RECLAIM_CLEAN:
@@ -1326,7 +1319,7 @@ static unsigned long shrink_page_list(struct list_head *page_list, 
			if (unlikely(PageTransHuge(page)))

				flags |= TTU_SPLIT_HUGE_PMD;

			if (!try_to_unmap(page, flags)) {

				nr_unmap_fail++;

				stat->nr_unmap_fail++;

				goto activate_locked;

			}

		}
@@ -1474,7 +1467,7 @@ activate_locked: 
		VM_BUG_ON_PAGE(PageActive(page), page);

		if (!PageMlocked(page)) {

			SetPageActive(page);

			pgactivate++;

			stat->nr_activate++;

			count_memcg_page_event(page, PGACTIVATE);

		}

keep_locked:
@@ -1489,18 +1482,8 @@ keep: 
	free_unref_page_list(&free_pages);



	list_splice(&ret_pages, page_list);

	count_vm_events(PGACTIVATE, pgactivate);



	if (stat) {

		stat->nr_dirty = nr_dirty;

		stat->nr_congested = nr_congested;

		stat->nr_unqueued_dirty = nr_unqueued_dirty;

		stat->nr_writeback = nr_writeback;

		stat->nr_immediate = nr_immediate;

		stat->nr_activate = pgactivate;

		stat->nr_ref_keep = nr_ref_keep;

		stat->nr_unmap_fail = nr_unmap_fail;

	}

	count_vm_events(PGACTIVATE, stat->nr_activate);



	return nr_reclaimed;

}
@@ -1512,6 +1495,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, 
		.priority = DEF_PRIORITY,

		.may_unmap = 1,

	};

	struct reclaim_stat dummy_stat;

	unsigned long ret;

	struct page *page, *next;

	LIST_HEAD(clean_pages);
@@ -1525,7 +1509,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone, 
	}



	ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,

			TTU_IGNORE_ACCESS, NULL, true);

			TTU_IGNORE_ACCESS, &dummy_stat, true);

	list_splice(&clean_pages, page_list);

	mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret);

	return ret;
@@ -1900,7 +1884,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, 
	unsigned long nr_scanned;

	unsigned long nr_reclaimed = 0;

	unsigned long nr_taken;

	struct reclaim_stat stat = {};

	struct reclaim_stat stat;

	int file = is_file_lru(lru);

	struct pglist_data *pgdat = lruvec_pgdat(lruvec);

	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;

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