From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator
Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts of
memory when booting a secondary kernel. Srikar Dronamraju reported that
multiple nodes may have no memory managed by the buddy allocator but still
return true for populated_zone().
Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of nodes")
was reported to cause kswapd to spin at 100% CPU usage when fadump was
enabled. The old code happened to deal with the situation of a populated
node with zero free pages by co-incidence but the current code tries to
reclaim populated zones without realising that is impossible.
We cannot just convert populated_zone() as many existing users really need
to check for present_pages. This patch introduces a managed_zone() helper
and uses it in the few cases where it is critical that the check is made
for managed pages -- zonelist construction and page reclaim.
Link: http://lkml.kernel.org/r/20160831195104.GB8119@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Tested-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 16 ++++++++++++++--
mm/page_alloc.c | 4 ++--
mm/vmscan.c | 22 +++++++++++-----------
3 files changed, 27 insertions(+), 15 deletions(-)
diff -puN include/linux/mmzone.h~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator include/linux/mmzone.h
--- a/include/linux/mmzone.h~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator
+++ a/include/linux/mmzone.h
@@ -828,9 +828,21 @@ unsigned long __init node_memmap_size_by
*/
#define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
-static inline int populated_zone(struct zone *zone)
+/*
+ * Returns true if a zone has pages managed by the buddy allocator.
+ * All the reclaim decisions have to use this function rather than
+ * populated_zone(). If the whole zone is reserved then we can easily
+ * end up with populated_zone() && !managed_zone().
+ */
+static inline bool managed_zone(struct zone *zone)
+{
+ return zone->managed_pages;
+}
+
+/* Returns true if a zone has memory */
+static inline bool populated_zone(struct zone *zone)
{
- return (!!zone->present_pages);
+ return zone->present_pages;
}
extern int movable_zone;
diff -puN mm/page_alloc.c~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator mm/page_alloc.c
--- a/mm/page_alloc.c~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator
+++ a/mm/page_alloc.c
@@ -4360,7 +4360,7 @@ static int build_zonelists_node(pg_data_
do {
zone_type--;
zone = pgdat->node_zones + zone_type;
- if (populated_zone(zone)) {
+ if (managed_zone(zone)) {
zoneref_set_zone(zone,
&zonelist->_zonerefs[nr_zones++]);
check_highest_zone(zone_type);
@@ -4598,7 +4598,7 @@ static void build_zonelists_in_zone_orde
for (j = 0; j < nr_nodes; j++) {
node = node_order[j];
z = &NODE_DATA(node)->node_zones[zone_type];
- if (populated_zone(z)) {
+ if (managed_zone(z)) {
zoneref_set_zone(z,
&zonelist->_zonerefs[pos++]);
check_highest_zone(zone_type);
diff -puN mm/vmscan.c~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-only-allocate-and-reclaim-from-zones-with-pages-managed-by-the-buddy-allocator
+++ a/mm/vmscan.c
@@ -1665,7 +1665,7 @@ static bool inactive_reclaimable_pages(s
for (zid = sc->reclaim_idx; zid >= 0; zid--) {
zone = &pgdat->node_zones[zid];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_page_state_snapshot(zone, NR_ZONE_LRU_BASE +
@@ -2036,7 +2036,7 @@ static bool inactive_list_is_low(struct
struct zone *zone = &pgdat->node_zones[zid];
unsigned long inactive_zone, active_zone;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
inactive_zone = zone_page_state(zone,
@@ -2171,7 +2171,7 @@ static void get_scan_count(struct lruvec
for (z = 0; z < MAX_NR_ZONES; z++) {
struct zone *zone = &pgdat->node_zones[z];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
total_high_wmark += high_wmark_pages(zone);
@@ -2510,7 +2510,7 @@ static inline bool should_continue_recla
/* If compaction would go ahead or the allocation would succeed, stop */
for (z = 0; z <= sc->reclaim_idx; z++) {
struct zone *zone = &pgdat->node_zones[z];
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
@@ -2840,7 +2840,7 @@ static bool pfmemalloc_watermark_ok(pg_d
for (i = 0; i <= ZONE_NORMAL; i++) {
zone = &pgdat->node_zones[i];
- if (!populated_zone(zone) ||
+ if (!managed_zone(zone) ||
pgdat_reclaimable_pages(pgdat) == 0)
continue;
@@ -3141,7 +3141,7 @@ static bool prepare_kswapd_sleep(pg_data
for (i = 0; i <= classzone_idx; i++) {
struct zone *zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (!zone_balanced(zone, order, classzone_idx))
@@ -3169,7 +3169,7 @@ static bool kswapd_shrink_node(pg_data_t
sc->nr_to_reclaim = 0;
for (z = 0; z <= sc->reclaim_idx; z++) {
zone = pgdat->node_zones + z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX);
@@ -3242,7 +3242,7 @@ static int balance_pgdat(pg_data_t *pgda
if (buffer_heads_over_limit) {
for (i = MAX_NR_ZONES - 1; i >= 0; i--) {
zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
sc.reclaim_idx = i;
@@ -3262,7 +3262,7 @@ static int balance_pgdat(pg_data_t *pgda
*/
for (i = classzone_idx; i >= 0; i--) {
zone = pgdat->node_zones + i;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_balanced(zone, sc.order, classzone_idx))
@@ -3508,7 +3508,7 @@ void wakeup_kswapd(struct zone *zone, in
pg_data_t *pgdat;
int z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
return;
if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
@@ -3522,7 +3522,7 @@ void wakeup_kswapd(struct zone *zone, in
/* Only wake kswapd if all zones are unbalanced */
for (z = 0; z <= classzone_idx; z++) {
zone = pgdat->node_zones + z;
- if (!populated_zone(zone))
+ if (!managed_zone(zone))
continue;
if (zone_balanced(zone, order, classzone_idx))
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
