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-rw-r--r--mm/ksm.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index 33781de0b6bf..c2b2a94f9d67 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1296,6 +1296,18 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page)
slot = ksm_scan.mm_slot;
if (slot == &ksm_mm_head) {
+ /*
+ * A number of pages can hang around indefinitely on per-cpu
+ * pagevecs, raised page count preventing write_protect_page
+ * from merging them. Though it doesn't really matter much,
+ * it is puzzling to see some stuck in pages_volatile until
+ * other activity jostles them out, and they also prevented
+ * LTP's KSM test from succeeding deterministically; so drain
+ * them here (here rather than on entry to ksm_do_scan(),
+ * so we don't IPI too often when pages_to_scan is set low).
+ */
+ lru_add_drain_all();
+
root_unstable_tree = RB_ROOT;
spin_lock(&ksm_mmlist_lock);