Date:	Fri, 22 Jul 2016 11:51:46 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Michal Hocko <mhocko@...e.cz>,
	Vlastimil Babka <vbabka@...e.cz>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] mm: add per-zone lru list stat

On Thu, Jul 21, 2016 at 03:10:57PM +0100, Mel Gorman wrote:
> From: Minchan Kim <minchan@...nel.org>
> 
> While I did stress test with hackbench, I got OOM message frequently which
> didn't ever happen in zone-lru.
> 
> gfp_mask=0x26004c0(GFP_KERNEL|__GFP_REPEAT|__GFP_NOTRACK), order=0
> ..
> ..
>  [<c71a76e2>] __alloc_pages_nodemask+0xe52/0xe60
>  [<c71f31dc>] ? new_slab+0x39c/0x3b0
>  [<c71f31dc>] new_slab+0x39c/0x3b0
>  [<c71f4eca>] ___slab_alloc.constprop.87+0x6da/0x840
>  [<c763e6fc>] ? __alloc_skb+0x3c/0x260
>  [<c777e127>] ? _raw_spin_unlock_irq+0x27/0x60
>  [<c70cebfc>] ? trace_hardirqs_on_caller+0xec/0x1b0
>  [<c70a1506>] ? finish_task_switch+0xa6/0x220
>  [<c7219ee0>] ? poll_select_copy_remaining+0x140/0x140
>  [<c7201645>] __slab_alloc.isra.81.constprop.86+0x40/0x6d
>  [<c763e6fc>] ? __alloc_skb+0x3c/0x260
>  [<c71f525c>] kmem_cache_alloc+0x22c/0x260
>  [<c763e6fc>] ? __alloc_skb+0x3c/0x260
>  [<c763e6fc>] __alloc_skb+0x3c/0x260
>  [<c763eece>] alloc_skb_with_frags+0x4e/0x1a0
>  [<c7638d6a>] sock_alloc_send_pskb+0x16a/0x1b0
>  [<c770b581>] ? wait_for_unix_gc+0x31/0x90
>  [<c71cfb1d>] ? alloc_set_pte+0x2ad/0x310
>  [<c77084dd>] unix_stream_sendmsg+0x28d/0x340
>  [<c7634dad>] sock_sendmsg+0x2d/0x40
>  [<c7634e2c>] sock_write_iter+0x6c/0xc0
>  [<c7204a90>] __vfs_write+0xc0/0x120
>  [<c72053ab>] vfs_write+0x9b/0x1a0
>  [<c71cc4a9>] ? __might_fault+0x49/0xa0
>  [<c72062c4>] SyS_write+0x44/0x90
>  [<c70036c6>] do_fast_syscall_32+0xa6/0x1e0
>  [<c777ea2c>] sysenter_past_esp+0x45/0x74
> 
> Mem-Info:
> active_anon:104698 inactive_anon:105791 isolated_anon:192
>  active_file:433 inactive_file:283 isolated_file:22
>  unevictable:0 dirty:0 writeback:296 unstable:0
>  slab_reclaimable:6389 slab_unreclaimable:78927
>  mapped:474 shmem:0 pagetables:101426 bounce:0
>  free:10518 free_pcp:334 free_cma:0
> Node 0 active_anon:418792kB inactive_anon:423164kB active_file:1732kB inactive_file:1132kB unevictable:0kB isolated(anon):768kB isolated(file):88kB mapped:1896kB dirty:0kB writeback:1184kB shmem:0kB writeback_tmp:0kB unstable:0kB pages_scanned:1478632 all_unreclaimable? yes
> DMA free:3304kB min:68kB low:84kB high:100kB present:15992kB managed:15916kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:4088kB kernel_stack:0kB pagetables:2480kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> lowmem_reserve[]: 0 809 1965 1965
> Normal free:3436kB min:3604kB low:4504kB high:5404kB present:897016kB managed:858460kB mlocked:0kB slab_reclaimable:25556kB slab_unreclaimable:311712kB kernel_stack:164608kB pagetables:30844kB bounce:0kB free_pcp:620kB local_pcp:104kB free_cma:0kB
> lowmem_reserve[]: 0 0 9247 9247
> HighMem free:33808kB min:512kB low:1796kB high:3080kB present:1183736kB managed:1183736kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:372252kB bounce:0kB free_pcp:428kB local_pcp:72kB free_cma:0kB
> lowmem_reserve[]: 0 0 0 0
> DMA: 2*4kB (UM) 2*8kB (UM) 0*16kB 1*32kB (U) 1*64kB (U) 2*128kB (UM) 1*256kB (U) 1*512kB (M) 0*1024kB 1*2048kB (U) 0*4096kB = 3192kB
> Normal: 33*4kB (MH) 79*8kB (ME) 11*16kB (M) 4*32kB (M) 2*64kB (ME) 2*128kB (EH) 7*256kB (EH) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3244kB
> HighMem: 2590*4kB (UM) 1568*8kB (UM) 491*16kB (UM) 60*32kB (UM) 6*64kB (M) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 33064kB
> Node 0 hugepages_total=0 hugepages_free=0 hugepages_surp=0 hugepages_size=2048kB
> 25121 total pagecache pages
> 24160 pages in swap cache
> Swap cache stats: add 86371, delete 62211, find 42865/60187
> Free swap  = 4015560kB
> Total swap = 4192252kB
> 524186 pages RAM
> 295934 pages HighMem/MovableOnly
> 9658 pages reserved
> 0 pages cma reserved
> 
> The order-0 allocation for normal zone failed while there are a lot of
> reclaimable memory(i.e., anonymous memory with free swap). I wanted to
> analyze the problem but it was hard because we removed per-zone lru stat
> so I couldn't know how many of anonymous memory there are in normal/dma zone.
> 
> When we investigate OOM problem, reclaimable memory count is crucial stat
> to find a problem. Without it, it's hard to parse the OOM message so I
> believe we should keep it.
> 
> With per-zone lru stat,
> 
> gfp_mask=0x26004c0(GFP_KERNEL|__GFP_REPEAT|__GFP_NOTRACK), order=0
> 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
> 
> With that, we can see normal zone has a 86M reclaimable memory so we can
> know something goes wrong(I will fix the problem in next patch) in reclaim.
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Yep, makes sense to retain that insight into zones.

Acked-by: Johannes Weiner <hannes@...xchg.org>

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