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Subject[PATCH 4/4] mm: Generalize putback scan functions
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Date
This combines two similar functions move_active_pages_to_lru()
and putback_inactive_pages() into single move_pages_to_lru().
This remove duplicate code and makes object file size smaller.

Before:
text data bss dec hex filename
57082 4732 128 61942 f1f6 mm/vmscan.o
After:
text data bss dec hex filename
55112 4600 128 59840 e9c0 mm/vmscan.o

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
mm/vmscan.c | 124 ++++++++++++++++++++---------------------------------------
1 file changed, 41 insertions(+), 83 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 88fa71e4c28f..66e70cf1dd94 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1807,33 +1807,53 @@ static int too_many_isolated(struct pglist_data *pgdat, int file,
return isolated > inactive;
}

-static noinline_for_stack void
-putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
+/*
+ * This moves pages from @list to corresponding LRU list.
+ *
+ * We move them the other way if the page is referenced by one or more
+ * processes, from rmap.
+ *
+ * If the pages are mostly unmapped, the processing is fast and it is
+ * appropriate to hold zone_lru_lock across the whole operation. But if
+ * the pages are mapped, the processing is slow (page_referenced()) so we
+ * should drop zone_lru_lock around each page. It's impossible to balance
+ * this, so instead we remove the pages from the LRU while processing them.
+ * It is safe to rely on PG_active against the non-LRU pages in here because
+ * nobody will play with that bit on a non-LRU page.
+ *
+ * The downside is that we have to touch page->_refcount against each page.
+ * But we had to alter page->flags anyway.
+ *
+ * Returns the number of pages moved to the given lruvec.
+ */
+
+static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
+ struct list_head *list)
{
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ int nr_pages, nr_moved = 0;
LIST_HEAD(pages_to_free);
+ struct page *page;
+ enum lru_list lru;

- /*
- * Put back any unfreeable pages.
- */
- while (!list_empty(page_list)) {
- struct page *page = lru_to_page(page_list);
- int lru;
-
- VM_BUG_ON_PAGE(PageLRU(page), page);
- list_del(&page->lru);
+ while (!list_empty(list)) {
+ page = lru_to_page(list);
if (unlikely(!page_evictable(page))) {
+ list_del_init(&page->lru);
spin_unlock_irq(&pgdat->lru_lock);
putback_lru_page(page);
spin_lock_irq(&pgdat->lru_lock);
continue;
}
-
lruvec = mem_cgroup_page_lruvec(page, pgdat);

+ VM_BUG_ON_PAGE(PageLRU(page), page);
SetPageLRU(page);
lru = page_lru(page);
- add_page_to_lru_list(page, lruvec, lru);
+
+ nr_pages = hpage_nr_pages(page);
+ update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
+ list_move(&page->lru, &lruvec->lists[lru]);

if (put_page_testzero(page)) {
__ClearPageLRU(page);
@@ -1847,13 +1867,17 @@ putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
spin_lock_irq(&pgdat->lru_lock);
} else
list_add(&page->lru, &pages_to_free);
+ } else {
+ nr_moved += nr_pages;
}
}

/*
* To save our caller's stack, now use input list for pages to free.
*/
- list_splice(&pages_to_free, page_list);
+ list_splice(&pages_to_free, list);
+
+ return nr_moved;
}

/*
@@ -1945,7 +1969,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
reclaim_stat->recent_rotated[0] = stat.nr_activate[0];
reclaim_stat->recent_rotated[1] = stat.nr_activate[1];

- putback_inactive_pages(lruvec, &page_list);
+ move_pages_to_lru(lruvec, &page_list);

__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);

@@ -1982,72 +2006,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
return nr_reclaimed;
}

-/*
- * This moves pages from the active list to the inactive list.
- *
- * We move them the other way if the page is referenced by one or more
- * processes, from rmap.
- *
- * If the pages are mostly unmapped, the processing is fast and it is
- * appropriate to hold zone_lru_lock across the whole operation. But if
- * the pages are mapped, the processing is slow (page_referenced()) so we
- * should drop zone_lru_lock around each page. It's impossible to balance
- * this, so instead we remove the pages from the LRU while processing them.
- * It is safe to rely on PG_active against the non-LRU pages in here because
- * nobody will play with that bit on a non-LRU page.
- *
- * The downside is that we have to touch page->_refcount against each page.
- * But we had to alter page->flags anyway.
- *
- * Returns the number of pages moved to the given lru.
- */
-
-static unsigned move_active_pages_to_lru(struct lruvec *lruvec,
- struct list_head *list,
- enum lru_list lru)
-{
- struct pglist_data *pgdat = lruvec_pgdat(lruvec);
- LIST_HEAD(pages_to_free);
- struct page *page;
- int nr_pages;
- int nr_moved = 0;
-
- while (!list_empty(list)) {
- page = lru_to_page(list);
- lruvec = mem_cgroup_page_lruvec(page, pgdat);
-
- VM_BUG_ON_PAGE(PageLRU(page), page);
- SetPageLRU(page);
-
- nr_pages = hpage_nr_pages(page);
- update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
- list_move(&page->lru, &lruvec->lists[lru]);
-
- if (put_page_testzero(page)) {
- __ClearPageLRU(page);
- __ClearPageActive(page);
- del_page_from_lru_list(page, lruvec, lru);
-
- if (unlikely(PageCompound(page))) {
- spin_unlock_irq(&pgdat->lru_lock);
- mem_cgroup_uncharge(page);
- (*get_compound_page_dtor(page))(page);
- spin_lock_irq(&pgdat->lru_lock);
- } else
- list_add(&page->lru, &pages_to_free);
- } else {
- nr_moved += nr_pages;
- }
- }
-
- /*
- * To save our caller's stack, now use input list for pages to free.
- */
- list_splice(&pages_to_free, list);
-
- return nr_moved;
-}
-
static void shrink_active_list(unsigned long nr_to_scan,
struct lruvec *lruvec,
struct scan_control *sc,
@@ -2134,8 +2092,8 @@ static void shrink_active_list(unsigned long nr_to_scan,
*/
reclaim_stat->recent_rotated[file] += nr_rotated;

- nr_activate = move_active_pages_to_lru(lruvec, &l_active, lru);
- nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, lru - LRU_ACTIVE);
+ nr_activate = move_pages_to_lru(lruvec, &l_active);
+ nr_deactivate = move_pages_to_lru(lruvec, &l_inactive);
/* Keep all free pages are in l_active list */
list_splice(&l_inactive, &l_active);

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