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Subject[PATCH 08/10] vmscan: Setup pagevec as late as possible in shrink_inactive_list()
Date
shrink_inactive_list() sets up a pagevec to release unfreeable pages. It
uses significant amounts of stack doing this. This patch splits
shrink_inactive_list() to take the stack usage out of the main path so
that callers to writepage() do not contain an unused pagevec on the
stack.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
mm/vmscan.c | 93 +++++++++++++++++++++++++++++++++-------------------------
1 files changed, 53 insertions(+), 40 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a232ad6..9bc1ede 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1120,6 +1120,54 @@ static int too_many_isolated(struct zone *zone, int file,
}

/*
+ * TODO: Try merging with migrations version of putback_lru_pages
+ */
+static noinline void putback_lru_pages(struct zone *zone,
+ struct zone_reclaim_stat *reclaim_stat,
+ unsigned long nr_anon, unsigned long nr_file,
+ struct list_head *page_list)
+{
+ struct page *page;
+ struct pagevec pvec;
+
+ pagevec_init(&pvec, 1);
+
+ /*
+ * Put back any unfreeable pages.
+ */
+ spin_lock(&zone->lru_lock);
+ while (!list_empty(page_list)) {
+ int lru;
+ page = lru_to_page(page_list);
+ VM_BUG_ON(PageLRU(page));
+ list_del(&page->lru);
+ if (unlikely(!page_evictable(page, NULL))) {
+ spin_unlock_irq(&zone->lru_lock);
+ putback_lru_page(page);
+ spin_lock_irq(&zone->lru_lock);
+ continue;
+ }
+ SetPageLRU(page);
+ lru = page_lru(page);
+ add_page_to_lru_list(zone, page, lru);
+ if (is_active_lru(lru)) {
+ int file = is_file_lru(lru);
+ reclaim_stat->recent_rotated[file]++;
+ }
+ if (!pagevec_add(&pvec, page)) {
+ spin_unlock_irq(&zone->lru_lock);
+ __pagevec_release(&pvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+ }
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
+
+ spin_unlock_irq(&zone->lru_lock);
+ pagevec_release(&pvec);
+}
+
+/*
* shrink_inactive_list() is a helper for shrink_zone(). It returns the number
* of reclaimed pages
*/
@@ -1128,12 +1176,10 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
int file)
{
LIST_HEAD(page_list);
- struct pagevec pvec;
unsigned long nr_scanned;
unsigned long nr_reclaimed = 0;
struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
int lumpy_reclaim = 0;
- struct page *page;
unsigned long nr_taken;
unsigned long nr_active;
unsigned int count[NR_LRU_LISTS] = { 0, };
@@ -1160,8 +1206,6 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
else if (sc->order && sc->priority < DEF_PRIORITY - 2)
lumpy_reclaim = 1;

- pagevec_init(&pvec, 1);
-
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
nr_taken = sc->isolate_pages(nr_to_scan,
@@ -1177,8 +1221,10 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
__count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
}

- if (nr_taken == 0)
- goto done;
+ if (nr_taken == 0) {
+ spin_unlock_irq(&zone->lru_lock);
+ return 0;
+ }

nr_active = clear_active_flags(&page_list, count);
__count_vm_events(PGDEACTIVATE, nr_active);
@@ -1229,40 +1275,7 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);

- spin_lock(&zone->lru_lock);
- /*
- * Put back any unfreeable pages.
- */
- while (!list_empty(&page_list)) {
- int lru;
- page = lru_to_page(&page_list);
- VM_BUG_ON(PageLRU(page));
- list_del(&page->lru);
- if (unlikely(!page_evictable(page, NULL))) {
- spin_unlock_irq(&zone->lru_lock);
- putback_lru_page(page);
- spin_lock_irq(&zone->lru_lock);
- continue;
- }
- SetPageLRU(page);
- lru = page_lru(page);
- add_page_to_lru_list(zone, page, lru);
- if (is_active_lru(lru)) {
- int file = is_file_lru(lru);
- reclaim_stat->recent_rotated[file]++;
- }
- if (!pagevec_add(&pvec, page)) {
- spin_unlock_irq(&zone->lru_lock);
- __pagevec_release(&pvec);
- spin_lock_irq(&zone->lru_lock);
- }
- }
- __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
- __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
-
-done:
- spin_unlock_irq(&zone->lru_lock);
- pagevec_release(&pvec);
+ putback_lru_pages(zone, reclaim_stat, nr_anon, nr_file, &page_list);
return nr_reclaimed;
}

--
1.6.5


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