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