[PATCH 06/10] vmscan: Split shrink_zone to reduce stack usage

[Mel Gorman <mel@csn.ul.ie>]

shrink_zone() calculculates how many pages it needs to shrink from each
LRU list in a given pass. It uses a number of temporary variables to
work this out that then remain on the stack. This patch splits the
function so that some of the stack variables can be discarded.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---
 mm/vmscan.c |   29 +++++++++++++++++++----------
 1 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1ace7c6..a374879 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1595,19 +1595,14 @@ static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
 	return nr;
 }
 
-/*
- * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
- */
-static void shrink_zone(struct zone *zone, struct scan_control *sc)
+/* Calculate how many pages from each LRU list should be scanned */
+static void calc_scan_trybatch(struct zone *zone,
+				 struct scan_control *sc, unsigned long *nr)
 {
-	unsigned long nr[NR_LRU_LISTS];
-	unsigned long nr_to_scan;
-	unsigned long percent[2];	/* anon @ 0; file @ 1 */
 	enum lru_list l;
-	unsigned long nr_reclaimed = sc->nr_reclaimed;
-	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+	unsigned long percent[2];	/* anon @ 0; file @ 1 */
+	int noswap = 0 ;
 	struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
-	int noswap = 0;
 
 	/* If we have no swap space, do not bother scanning anon pages. */
 	if (!sc->may_swap || (nr_swap_pages <= 0)) {
@@ -1629,6 +1624,20 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc)
 		nr[l] = nr_scan_try_batch(scan,
 					  &reclaim_stat->nr_saved_scan[l]);
 	}
+}
+
+/*
+ * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
+ */
+static void shrink_zone(struct zone *zone, struct scan_control *sc)
+{
+	unsigned long nr[NR_LRU_LISTS];
+	unsigned long nr_to_scan;
+	unsigned long nr_reclaimed = sc->nr_reclaimed;
+	unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+	enum lru_list l;
+
+	calc_scan_trybatch(zone, sc, nr);
 
 	while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
 					nr[LRU_INACTIVE_FILE]) {
-- 
1.6.5

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