[RFC][PATCH 7/9] mm/vmscan: Consider anonymous pages without swap

Dave Hansen
2020-08-18T18:48:25Z

From: Keith Busch <kbusch@kernel.org>

Age and reclaim anonymous pages if a migration path is available. The
node has other recourses for inactive anonymous pages beyond swap,

#Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Keith Busch <kbusch@kernel.org>
[vishal: fixup the migration->demotion rename]
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>

--

Changes from Dave 06/2020:
* rename reclaim_anon_pages()->can_reclaim_anon_pages()

Note: Keith's Intel SoB is commented out because he is no
longer at Intel and his @intel.com mail will bouncee
---

b/include/linux/node.h | 9 +++++++++
b/mm/vmscan.c | 33 ++++++++++++++++++++++++++++-----
2 files changed, 37 insertions(+), 5 deletions(-)

diff -puN include/linux/node.h~0009-mm-vmscan-Consider-anonymous-pages-without-swap include/linux/node.h
--- a/include/linux/node.h~0009-mm-vmscan-Consider-anonymous-pages-without-swap 2020-08-18 11:36:55.284583173 -0700
+++ b/include/linux/node.h 2020-08-18 11:36:55.290583173 -0700
@@ -180,4 +180,13 @@ static inline void register_hugetlbfs_wi

#define to_node(device) container_of(device, struct node, dev)

+#ifdef CONFIG_MIGRATION
+extern int next_demotion_node(int node);
+#else
+static inline int next_demotion_node(int node)
+{
+ return NUMA_NO_NODE;
+}
+#endif
+
#endif /* _LINUX_NODE_H_ */
diff -puN mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap mm/vmscan.c
--- a/mm/vmscan.c~0009-mm-vmscan-Consider-anonymous-pages-without-swap 2020-08-18 11:36:55.286583173 -0700
+++ b/mm/vmscan.c 2020-08-18 11:36:55.292583173 -0700
@@ -295,6 +295,26 @@ static bool writeback_throttling_sane(st
}
#endif

+static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
+ int node_id)
+{
+ /* Always age anon pages when we have swap */
+ if (memcg == NULL) {
+ if (get_nr_swap_pages() > 0)
+ return true;
+ } else {
+ if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
+ return true;
+ }
+
+ /* Also age anon pages if we can auto-migrate them */
+ if (next_demotion_node(node_id) >= 0)
+ return true;
+
+ /* No way to reclaim anon pages */
+ return false;
+}
+
/*
* This misses isolated pages which are not accounted for to save counters.
* As the data only determines if reclaim or compaction continues, it is
@@ -306,7 +326,7 @@ unsigned long zone_reclaimable_pages(str

nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
- if (get_nr_swap_pages() > 0)
+ if (can_reclaim_anon_pages(NULL, zone_to_nid(zone)))
nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);

@@ -2338,6 +2358,7 @@ enum scan_balance {
static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
unsigned long *nr)
{
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
unsigned long anon_cost, file_cost, total_cost;
int swappiness = mem_cgroup_swappiness(memcg);
@@ -2348,7 +2369,7 @@ 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 (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id)) {
scan_balance = SCAN_FILE;
goto out;
}
@@ -2631,7 +2652,9 @@ static void shrink_lruvec(struct lruvec
* Even if we did not try to evict anon pages at all, we want to
* rebalance the anon lru active/inactive ratio.
*/
- if (total_swap_pages && inactive_is_low(lruvec, LRU_INACTIVE_ANON))
+ if (can_reclaim_anon_pages(lruvec_memcg(lruvec),
+ lruvec_pgdat(lruvec)->node_id) &&
+ inactive_is_low(lruvec, LRU_INACTIVE_ANON))
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
sc, LRU_ACTIVE_ANON);
}
@@ -2701,7 +2724,7 @@ static inline bool should_continue_recla
*/
pages_for_compaction = compact_gap(sc->order);
inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE);
- if (get_nr_swap_pages() > 0)
+ if (can_reclaim_anon_pages(NULL, pgdat->node_id))
inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON);

return inactive_lru_pages > pages_for_compaction;
@@ -3462,7 +3485,7 @@ static void age_active_anon(struct pglis
struct mem_cgroup *memcg;
struct lruvec *lruvec;

- if (!total_swap_pages)
+ if (!can_reclaim_anon_pages(NULL, pgdat->node_id))
return;

lruvec = mem_cgroup_lruvec(NULL, pgdat);
_