From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Anonymous pages are kept on their own LRU(s). These lists could
theoretically always be scanned and maintained. But, without swap,
there is currently nothing the kernel can *do* with the results of a
scanned, sorted LRU for anonymous pages.
A check for '!total_swap_pages' currently serves as a valid check as
to whether anonymous LRUs should be maintained. However, another
method will be added shortly: page demotion.
Abstract out the 'total_swap_pages' checks into a helper, give it a
logically significant name, and check for the possibility of page
demotion.
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Reviewed-by: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: osalvador <osalvador@xxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Changes since 20210618:
* Rename function per Oscar's comments.
* Change parameter per Wei's comments.
* Make the function static.
* Consider whether demotion is disabled.
---
mm/vmscan.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 78b3bae71520..55f6192b2a51 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2716,6 +2716,26 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
}
}
+/*
+ * Anonymous LRU management is a waste if there is
+ * ultimately no way to reclaim the memory.
+ */
+static bool anon_can_be_aged(struct pglist_data *pgdat,
+ struct scan_control *sc)
+{
+ /* Aging the anon LRU is valuable if swap is present: */
+ if (total_swap_pages > 0)
+ return true;
+
+ /* Also valuable if anon pages can be demoted: */
+ if (!sc->no_demotion &&
+ next_demotion_node(pgdat->node_id) != NUMA_NO_NODE)
+ return true;
+
+ /* No way to reclaim anon pages. Should not age anon LRUs: */
+ return false;
+}
+
static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
{
unsigned long nr[NR_LRU_LISTS];
@@ -2825,7 +2845,8 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
* 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 (anon_can_be_aged(lruvec_pgdat(lruvec), sc) &&
+ inactive_is_low(lruvec, LRU_INACTIVE_ANON))
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,
sc, LRU_ACTIVE_ANON);
}
@@ -3654,7 +3675,7 @@ static void age_active_anon(struct pglist_data *pgdat,
struct mem_cgroup *memcg;
struct lruvec *lruvec;
- if (!total_swap_pages)
+ if (!anon_can_be_aged(pgdat, sc))
return;
lruvec = mem_cgroup_lruvec(NULL, pgdat);
--
2.30.2
