It was hard to explain the page counts which were causing new LTP tests of KSM to fail: we need to drain the per-cpu pagevecs to LRU occasionally. Reported-by: CAI Qian <caiqian@xxxxxxxxxx> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> --- mm/ksm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- 2.6.37/mm/ksm.c 2010-12-24 19:31:45.000000000 -0800 +++ linux/mm/ksm.c 2011-01-02 15:06:52.000000000 -0800 @@ -1247,6 +1247,18 @@ static struct rmap_item *scan_get_next_r 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); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>