[RFC][PATCH v2 21/21] mm/vmscan.c: shrink anon list if can migrate to PMEM

[Fengguang Wu]

Fix OOM by making in-kernel DRAM=>PMEM migration reachable.

Here we assume these 2 possible demotion paths:
- DRAM migrate to PMEM
- PMEM to swap device

Signed-off-by: Fengguang Wu <fengguang...@intel.com>
---
 mm/vmscan.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- linux.orig/mm/vmscan.c      2018-12-23 20:38:44.310446223 +0800
+++ linux/mm/vmscan.c   2018-12-23 20:38:44.306446146 +0800
@@ -2259,7 +2259,7 @@ static bool inactive_list_is_low(struct
         * If we don't have swap space, anonymous page deactivation
         * is pointless.
         */
-       if (!file && !total_swap_pages)
+       if (!file && (is_node_pmem(pgdat->node_id) && !total_swap_pages))
                return false;
 
        inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx);
@@ -2340,7 +2340,8 @@ static void get_scan_count(struct lruvec
        enum lru_list lru;
 
        /* If we have no swap space, do not bother scanning anon pages. */
-       if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) {
+       if (is_node_pmem(pgdat->node_id) &&
+           (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0)) {
                scan_balance = SCAN_FILE;
                goto out;
        }