[PATCH 4/5] mm: consider per-zone inactive ratio to deactivate

From: Mel Gorman
Date: Thu Jul 21 2016 - 10:11:54 EST

From: Minchan Kim <minchan@xxxxxxxxxx>

Minchan Kim reported that with per-zone lru state it was possible to
identify that a normal zone with 8^M anonymous pages could trigger
OOM with non-atomic order-0 allocations as all pages in the zone
were in the active list.

gfp_mask=0x26004c0(GFP_KERNEL|__GFP_REPEAT|__GFP_NOTRACK), order=0
Call Trace:
[<c51a76e2>] __alloc_pages_nodemask+0xe52/0xe60
[<c51f31dc>] ? new_slab+0x39c/0x3b0
[<c51f31dc>] new_slab+0x39c/0x3b0
[<c51f4eca>] ___slab_alloc.constprop.87+0x6da/0x840
[<c563e6fc>] ? __alloc_skb+0x3c/0x260
[<c50b8e93>] ? enqueue_task_fair+0x73/0xbf0
[<c5219ee0>] ? poll_select_copy_remaining+0x140/0x140
[<c5201645>] __slab_alloc.isra.81.constprop.86+0x40/0x6d
[<c563e6fc>] ? __alloc_skb+0x3c/0x260
[<c51f525c>] kmem_cache_alloc+0x22c/0x260
[<c563e6fc>] ? __alloc_skb+0x3c/0x260
[<c563e6fc>] __alloc_skb+0x3c/0x260
[<c563eece>] alloc_skb_with_frags+0x4e/0x1a0
[<c5638d6a>] sock_alloc_send_pskb+0x16a/0x1b0
[<c570b581>] ? wait_for_unix_gc+0x31/0x90
[<c57084dd>] unix_stream_sendmsg+0x28d/0x340
[<c5634dad>] sock_sendmsg+0x2d/0x40
[<c5634e2c>] sock_write_iter+0x6c/0xc0
[<c5204a90>] __vfs_write+0xc0/0x120
[<c52053ab>] vfs_write+0x9b/0x1a0
[<c51cc4a9>] ? __might_fault+0x49/0xa0
[<c52062c4>] SyS_write+0x44/0x90
[<c50036c6>] do_fast_syscall_32+0xa6/0x1e0

active_anon:101103 inactive_anon:102219 isolated_anon:0
active_file:503 inactive_file:544 isolated_file:0
unevictable:0 dirty:0 writeback:34 unstable:0
slab_reclaimable:6298 slab_unreclaimable:74669
mapped:863 shmem:0 pagetables:100998 bounce:0
free:23573 free_pcp:1861 free_cma:0
Node 0 active_anon:404412kB inactive_anon:409040kB active_file:2012kB inactive_file:2176kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:3452kB dirty:0kB writeback:136kB shmem:0kB writeback_tmp:0kB unstable:0kB pages_scanned:1320845 all_unreclaimable? yes
DMA free:3296kB min:68kB low:84kB high:100kB active_anon:5540kB inactive_anon:0kB active_file:0kB inactive_file:0kB present:15992kB managed:15916kB mlocked:0kB slab_reclaimable:248kB slab_unreclaimable:2628kB kernel_stack:792kB pagetables:2316kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
lowmem_reserve[]: 0 809 1965 1965
Normal free:3600kB min:3604kB low:4504kB high:5404kB active_anon:86304kB inactive_anon:0kB active_file:160kB inactive_file:376kB present:897016kB managed:858524kB mlocked:0kB slab_reclaimable:24944kB slab_unreclaimable:296048kB kernel_stack:163832kB pagetables:35892kB bounce:0kB free_pcp:3076kB local_pcp:656kB free_cma:0kB
lowmem_reserve[]: 0 0 9247 9247
HighMem free:86156kB min:512kB low:1796kB high:3080kB active_anon:312852kB inactive_anon:410024kB active_file:1924kB inactive_file:2012kB present:1183736kB managed:1183736kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:365784kB bounce:0kB free_pcp:3868kB local_pcp:720kB free_cma:0kB
lowmem_reserve[]: 0 0 0 0
DMA: 8*4kB (UM) 8*8kB (UM) 4*16kB (M) 2*32kB (UM) 2*64kB (UM) 1*128kB (M) 3*256kB (UME) 2*512kB (UE) 1*1024kB (E) 0*2048kB 0*4096kB = 3296kB
Normal: 240*4kB (UME) 160*8kB (UME) 23*16kB (ME) 3*32kB (UE) 3*64kB (UME) 2*128kB (ME) 1*256kB (U) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3408kB
HighMem: 10942*4kB (UM) 3102*8kB (UM) 866*16kB (UM) 76*32kB (UM) 11*64kB (UM) 4*128kB (UM) 1*256kB (M) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 86344kB
Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
54409 total pagecache pages
53215 pages in swap cache
Swap cache stats: add 300982, delete 247765, find 157978/226539
Free swap = 3803244kB
Total swap = 4192252kB
524186 pages RAM
295934 pages HighMem/MovableOnly
9642 pages reserved
0 pages cma reserved

The problem is due to the active deactivation logic in inactive_list_is_low.

Node 0 active_anon:404412kB inactive_anon:409040kB

IOW, (inactive_anon of node * inactive_ratio > active_anon of node) due to
highmem anonymous stat so VM never deactivates normal zone's anonymous pages.

This patch is a modified version of Minchan's original solution but based
upon it. The problem with Minchan's patch is that it didn't take memcg
into account and any low zone with an imbalanced list could force a rotation.

In this patch, a zone-constrained global reclaim will rotate the list if
the inactive/active ratio of all eligible zones needs to be corrected. It
is possible that higher zone pages will be initially rotated prematurely
but this is the safer choice to maintain overall LRU age.

Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
mm/vmscan.c | 37 ++++++++++++++++++++++++++++++++-----
1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 134381a20099..6810d81f60c7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1964,7 +1964,8 @@ static void shrink_active_list(unsigned long nr_to_scan,
* 1TB 101 10GB
* 10TB 320 32GB
-static bool inactive_list_is_low(struct lruvec *lruvec, bool file)
+static bool inactive_list_is_low(struct lruvec *lruvec, bool file,
+ struct scan_control *sc)
unsigned long inactive_ratio;
unsigned long inactive;
@@ -1981,6 +1982,32 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file)
inactive = lruvec_lru_size(lruvec, file * LRU_FILE);
active = lruvec_lru_size(lruvec, file * LRU_FILE + LRU_ACTIVE);

+ /*
+ * For global reclaim on zone-constrained allocations, it is necessary
+ * to check if rotations are required for lowmem to be reclaimed. This
+ * calculates the inactive/active pages available in eligible zones.
+ */
+ if (global_reclaim(sc)) {
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+ int zid;
+ for (zid = sc->reclaim_idx + 1; zid < MAX_NR_ZONES; zid++) {
+ struct zone *zone = &pgdat->node_zones[zid];
+ unsigned long inactive_zone, active_zone;
+ if (!populated_zone(zone))
+ continue;
+ inactive_zone = zone_page_state(zone,
+ NR_ZONE_LRU_BASE + (file * LRU_FILE));
+ active_zone = zone_page_state(zone,
+ inactive -= min(inactive, inactive_zone);
+ active -= min(active, active_zone);
+ }
+ }
gb = (inactive + active) >> (30 - PAGE_SHIFT);
if (gb)
inactive_ratio = int_sqrt(10 * gb);
@@ -1994,7 +2021,7 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
struct lruvec *lruvec, struct scan_control *sc)
if (is_active_lru(lru)) {
- if (inactive_list_is_low(lruvec, is_file_lru(lru)))
+ if (inactive_list_is_low(lruvec, is_file_lru(lru), sc))
shrink_active_list(nr_to_scan, lruvec, sc, lru);
return 0;
@@ -2125,7 +2152,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
* lruvec even if it has plenty of old anonymous pages unless the
* system is under heavy pressure.
- if (!inactive_list_is_low(lruvec, true) &&
+ if (!inactive_list_is_low(lruvec, true, sc) &&
lruvec_lru_size(lruvec, LRU_INACTIVE_FILE) >> sc->priority) {
scan_balance = SCAN_FILE;
goto out;
@@ -2367,7 +2394,7 @@ static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memc
* Even if we did not try to evict anon pages at all, we want to
* rebalance the anon lru active/inactive ratio.
- if (inactive_list_is_low(lruvec, false))
+ if (inactive_list_is_low(lruvec, false, sc))
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,

@@ -3020,7 +3047,7 @@ static void age_active_anon(struct pglist_data *pgdat,
do {
struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg);

- if (inactive_list_is_low(lruvec, false))
+ if (inactive_list_is_low(lruvec, false, sc))
shrink_active_list(SWAP_CLUSTER_MAX, lruvec,