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Date: Thu, 11 May 2017 09:20:15 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Minchan Kim <minchan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Johannes Weiner <hannes@...xchg.org>,
Mel Gorman <mgorman@...hsingularity.net>,
kernel-team <kernel-team@....com>
Subject: Re: [PATCH v2] mm: vmscan: scan until it founds eligible pages
On Thu 11-05-17 08:00:32, Minchan Kim wrote:
> Although there are a ton of free swap and anonymous LRU page
> in elgible zones, OOM happened.
>
> balloon invoked oom-killer: gfp_mask=0x17080c0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_NOTRACK), nodemask=(null), order=0, oom_score_adj=0
> CPU: 7 PID: 1138 Comm: balloon Not tainted 4.11.0-rc6-mm1-zram-00289-ge228d67e9677-dirty #17
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
> Call Trace:
> dump_stack+0x65/0x87
> dump_header.isra.19+0x8f/0x20f
> ? preempt_count_add+0x9e/0xb0
> ? _raw_spin_unlock_irqrestore+0x24/0x40
> oom_kill_process+0x21d/0x3f0
> ? has_capability_noaudit+0x17/0x20
> out_of_memory+0xd8/0x390
> __alloc_pages_slowpath+0xbc1/0xc50
> ? anon_vma_interval_tree_insert+0x84/0x90
> __alloc_pages_nodemask+0x1a5/0x1c0
> pte_alloc_one+0x20/0x50
> __pte_alloc+0x1e/0x110
> __handle_mm_fault+0x919/0x960
> handle_mm_fault+0x77/0x120
> __do_page_fault+0x27a/0x550
> trace_do_page_fault+0x43/0x150
> do_async_page_fault+0x2c/0x90
> async_page_fault+0x28/0x30
> RIP: 0033:0x7fc4636bacb8
> RSP: 002b:00007fff97c9c4c0 EFLAGS: 00010202
> RAX: 00007fc3e818d000 RBX: 00007fc4639f8760 RCX: 00007fc46372e9ca
> RDX: 0000000000101002 RSI: 0000000000101000 RDI: 0000000000000000
> RBP: 0000000000100010 R08: 00000000ffffffff R09: 0000000000000000
> R10: 0000000000000022 R11: 00000000000a3901 R12: 00007fc3e818d010
> R13: 0000000000101000 R14: 00007fc4639f87b8 R15: 00007fc4639f87b8
> Mem-Info:
> active_anon:424716 inactive_anon:65314 isolated_anon:0
> active_file:52 inactive_file:46 isolated_file:0
> unevictable:0 dirty:27 writeback:0 unstable:0
> slab_reclaimable:3967 slab_unreclaimable:4125
> mapped:133 shmem:43 pagetables:1674 bounce:0
> free:4637 free_pcp:225 free_cma:0
> Node 0 active_anon:1698864kB inactive_anon:261256kB active_file:208kB inactive_file:184kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:532kB dirty:108kB writeback:0kB shmem:172kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
> DMA free:7316kB min:32kB low:44kB high:56kB active_anon:8064kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15992kB managed:15908kB mlocked:0kB slab_reclaimable:464kB slab_unreclaimable:40kB kernel_stack:0kB pagetables:24kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> lowmem_reserve[]: 0 992 992 1952
> DMA32 free:9088kB min:2048kB low:3064kB high:4080kB active_anon:952176kB inactive_anon:0kB active_file:36kB inactive_file:0kB unevictable:0kB writepending:88kB present:1032192kB managed:1019388kB mlocked:0kB slab_reclaimable:13532kB slab_unreclaimable:16460kB kernel_stack:3552kB pagetables:6672kB bounce:0kB free_pcp:56kB local_pcp:24kB free_cma:0kB
> lowmem_reserve[]: 0 0 0 959
> Movable free:3644kB min:1980kB low:2960kB high:3940kB active_anon:738560kB inactive_anon:261340kB active_file:188kB inactive_file:640kB unevictable:0kB writepending:20kB present:1048444kB managed:1010816kB mlocked:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB bounce:0kB free_pcp:832kB local_pcp:60kB free_cma:0kB
> lowmem_reserve[]: 0 0 0 0
> DMA: 1*4kB (E) 0*8kB 18*16kB (E) 10*32kB (E) 10*64kB (E) 9*128kB (ME) 8*256kB (E) 2*512kB (E) 2*1024kB (E) 0*2048kB 0*4096kB = 7524kB
> DMA32: 417*4kB (UMEH) 181*8kB (UMEH) 68*16kB (UMEH) 48*32kB (UMEH) 14*64kB (MH) 3*128kB (M) 1*256kB (H) 1*512kB (M) 2*1024kB (M) 0*2048kB 0*4096kB = 9836kB
> Movable: 1*4kB (M) 1*8kB (M) 1*16kB (M) 1*32kB (M) 0*64kB 1*128kB (M) 2*256kB (M) 4*512kB (M) 1*1024kB (M) 0*2048kB 0*4096kB = 3772kB
> 378 total pagecache pages
> 17 pages in swap cache
> Swap cache stats: add 17325, delete 17302, find 0/27
> Free swap = 978940kB
> Total swap = 1048572kB
> 524157 pages RAM
> 0 pages HighMem/MovableOnly
> 12629 pages reserved
> 0 pages cma reserved
> 0 pages hwpoisoned
> [ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
> [ 433] 0 433 4904 5 14 3 82 0 upstart-udev-br
> [ 438] 0 438 12371 5 27 3 191 -1000 systemd-udevd
>
> With investigation, skipping page of isolate_lru_pages makes reclaim
> void because it returns zero nr_taken easily so LRU shrinking is
> effectively nothing and just increases priority aggressively.
> Finally, OOM happens.
>
> The problem is that get_scan_count determines nr_to_scan with
> eligible zones so although priority drops to zero, it couldn't
> reclaim any pages if the LRU contains mostly ineligible pages.
>
> get_scan_count:
>
> size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
> size = size >> sc->priority;
>
> Assumes sc->priority is 0 and LRU list is as follows.
>
> N-N-N-N-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H-H
>
> (Ie, small eligible pages are in the head of LRU but others are
> almost ineligible pages)
>
> In that case, size becomes 4 so VM want to scan 4 pages but 4 pages
> from tail of the LRU are not eligible pages.
> If get_scan_count counts skipped pages, it doesn't reclaim any pages
> remained after scanning 4 pages so it ends up OOM happening.
>
> This patch makes isolate_lru_pages try to scan pages until it
> encounters eligible zones's pages.
>
Fixes: 3db65812d688 ("Revert "mm, vmscan: account for skipped pages as a partial scan"")
> Signed-off-by: Minchan Kim <minchan@...nel.org>
Acked-by: Michal Hocko <mhocko@...e.com>
> ---
> * from v1
> * put more words in description and code
> * drop unncessary pages_skipped list flushing
>
> mm/vmscan.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 5ebf468c5429..e051bf4a1144 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1449,7 +1449,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
> *
> * Appropriate locks must be held before calling this function.
> *
> - * @nr_to_scan: The number of pages to look through on the list.
> + * @nr_to_scan: The number of eligible pages to look through on the list.
> * @lruvec: The LRU vector to pull pages from.
> * @dst: The temp list to put pages on to.
> * @nr_scanned: The number of pages that were scanned.
> @@ -1469,11 +1469,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
> unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
> unsigned long skipped = 0;
> - unsigned long scan, nr_pages;
> + unsigned long scan, total_scan, nr_pages;
> LIST_HEAD(pages_skipped);
>
> - for (scan = 0; scan < nr_to_scan && nr_taken < nr_to_scan &&
> - !list_empty(src); scan++) {
> + for (total_scan = scan = 0; scan < nr_to_scan &&
> + nr_taken < nr_to_scan &&
> + !list_empty(src);
> + total_scan++) {
> struct page *page;
>
> page = lru_to_page(src);
> @@ -1487,6 +1489,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> continue;
> }
>
> + /*
> + * Do not count skipped pages because it makes the function to
> + * return with none isolated pages if the LRU mostly contains
> + * ineligible pages so that VM cannot reclaim any pages and
> + * trigger premature OOM.
> + */
> + scan++;
> switch (__isolate_lru_page(page, mode)) {
> case 0:
> nr_pages = hpage_nr_pages(page);
> @@ -1524,9 +1533,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> skipped += nr_skipped[zid];
> }
> }
> - *nr_scanned = scan;
> + *nr_scanned = total_scan;
> trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
> - scan, skipped, nr_taken, mode, lru);
> + total_scan, skipped, nr_taken, mode, lru);
> update_lru_sizes(lruvec, lru, nr_zone_taken);
> return nr_taken;
> }
> --
> 2.7.4
>
--
Michal Hocko
SUSE Labs
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