Hi Mel,
On Wed, Jul 20, 2016 at 04:21:51PM +0100, Mel Gorman wrote:
> 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
>
> Mem-Info:
> 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.
Could you explan why we should consider memcg here?
>
> In this page, a zone-constrained global reclaim will rotate the list if
patch,
> 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 8f5959469079..dddf73f4293c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1976,7 +1976,8 @@ 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;
> @@ -1993,6 +1994,32 @@ 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; 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,
> + NR_ZONE_LRU_BASE + (file * LRU_FILE) + LRU_ACTIVE);
> +
> + inactive -= min(inactive, inactive_zone);
> + active -= min(active, active_zone);
> + }
> + }
> +
> gb = (inactive + active) >> (30 - PAGE_SHIFT);
> if (gb)
> inactive_ratio = int_sqrt(10 * gb);
> @@ -2006,7 +2033,7 @@ 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;
> }
> @@ -2137,7 +2164,7 @@ 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;
> @@ -2379,7 +2406,7 @@ 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,
> sc, LRU_ACTIVE_ANON);
>
> @@ -3032,7 +3059,7 @@ 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,
> sc, LRU_ACTIVE_ANON);
>
> --
> 2.6.4
>
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