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mm, vmscan: only allocate and reclaim from zones with pages managed b…
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…y 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 1d82de6 ("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/[email protected]
Signed-off-by: Mel Gorman <[email protected]>
Reported-by: Srikar Dronamraju <[email protected]>
Tested-by: Srikar Dronamraju <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@gormanm @torvalds
gormanm authored and torvalds committed Sep 2, 2016
1 parent e6173ba commit 6aa303d
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Showing 3 changed files with 27 additions and 15 deletions.
16 changes: 14 additions & 2 deletions include/linux/mmzone.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -828,9 +828,21 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
*/
#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;
Expand Down
4 changes: 2 additions & 2 deletions mm/page_alloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4360,7 +4360,7 @@ static int build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist,
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);
Expand Down Expand Up @@ -4598,7 +4598,7 @@ static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
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);
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22 changes: 11 additions & 11 deletions mm/vmscan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1665,7 +1665,7 @@ static bool inactive_reclaimable_pages(struct lruvec *lruvec,

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 +
Expand Down Expand Up @@ -2036,7 +2036,7 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
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,
Expand Down Expand Up @@ -2171,7 +2171,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,

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);
Expand Down Expand Up @@ -2510,7 +2510,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
/* 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)) {
Expand Down Expand Up @@ -2840,7 +2840,7 @@ static bool pfmemalloc_watermark_ok(pg_data_t *pgdat)

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;

Expand Down Expand Up @@ -3141,7 +3141,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx)
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))
Expand Down Expand Up @@ -3169,7 +3169,7 @@ static bool kswapd_shrink_node(pg_data_t *pgdat,
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);
Expand Down Expand Up @@ -3242,7 +3242,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
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;
Expand All @@ -3262,7 +3262,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
*/
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))
Expand Down Expand Up @@ -3508,7 +3508,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
pg_data_t *pgdat;
int z;

if (!populated_zone(zone))
if (!managed_zone(zone))
return;

if (!cpuset_zone_allowed(zone, GFP_KERNEL | __GFP_HARDWALL))
Expand All @@ -3522,7 +3522,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
/* 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))
Expand Down

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