OOM-Killer crash

Hi,
I noticed that my apache server in a ubuntu lxc stops working on a regular basis during the last few days usually in the morning. The error messages in the lxc instance look like this (oom-killer invoked by btrfs). Does anyone know how to fix this recurring error? Cheers

    Aug 15 06:29:21 zeus kernel: [244139.356579] btrfs-transacti invoked oom-killer: gfp_mask=0x2400840, order=0, oom_score_adj=0
    Aug 15 06:29:21 zeus kernel: [244139.356586] btrfs-transacti cpuset=/ mems_allowed=0
    Aug 15 06:29:21 zeus kernel: [244139.356597] CPU: 0 PID: 3675 Comm: btrfs-transacti Not tainted 4.4.79-967673b9d511e4292e3bcb76c9e064bc-0 #1
    Aug 15 06:29:21 zeus kernel: [244139.356601] Hardware name: Marvell Armada 380/385 (Device Tree)
    Aug 15 06:29:21 zeus kernel: [244139.356604] Backtrace:
    Aug 15 06:29:21 zeus kernel: [244139.356616] [<c001c66c>] (dump_backtrace) from [<c001c85c>] (show_stack+0x18/0x1c)
    Aug 15 06:29:21 zeus kernel: [244139.356619]  r6:00000000 r5:60000013 r4:c06c0368 r3:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356631] [<c001c844>] (show_stack) from [<c02f1598>] (dump_stack+0x98/0xac)
    Aug 15 06:29:21 zeus kernel: [244139.356638] [<c02f1500>] (dump_stack) from [<c00a9414>] (dump_header+0x5c/0x1ac)
    Aug 15 06:29:21 zeus kernel: [244139.356641]  r6:e9fcfb1c r5:00000000 r4:00000214 r3:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356651] [<c00a93b8>] (dump_header) from [<c00a9c6c>] (oom_kill_process+0x36c/0x4a4)
    Aug 15 06:29:21 zeus kernel: [244139.356654]  r10:c06b5068 r9:00001386 r8:c06b5068 r7:00000009 r6:0007e63c r5:e9fcfb1c
    Aug 15 06:29:21 zeus kernel: [244139.356662]  r4:e8a37180
    Aug 15 06:29:21 zeus kernel: [244139.356668] [<c00a9900>] (oom_kill_process) from [<c00aa10c>] (out_of_memory+0x2f8/0x340)
    Aug 15 06:29:21 zeus kernel: [244139.356671]  r10:c06b5068 r9:00001386 r8:c06b5068 r7:c06b51e4 r6:0007e63c r5:e881a00c
    Aug 15 06:29:21 zeus kernel: [244139.356679]  r4:e9fcfb1c
    Aug 15 06:29:21 zeus kernel: [244139.356687] [<c00a9e14>] (out_of_memory) from [<c00ae198>] (__alloc_pages_nodemask+0x734/0x86c)
    Aug 15 06:29:21 zeus kernel: [244139.356689]  r10:e9fce000 r9:00000000 r8:00000002 r7:c06b0d5c r6:02400840 r5:00000040
    Aug 15 06:29:21 zeus kernel: [244139.356697]  r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356704] [<c00ada64>] (__alloc_pages_nodemask) from [<c00a6344>] (pagecache_get_page+0x78/0x1f8)
    Aug 15 06:29:21 zeus kernel: [244139.356706]  r10:c06b4a5e r9:00012e49 r8:c06b0f70 r7:030c5e02 r6:ea8a7f54 r5:02400840
    Aug 15 06:29:21 zeus kernel: [244139.356714]  r4:00000007
    Aug 15 06:29:21 zeus kernel: [244139.356722] [<c00a62cc>] (pagecache_get_page) from [<c024ff74>] (alloc_extent_buffer+0xcc/0x3c8)
    Aug 15 06:29:21 zeus kernel: [244139.356725]  r10:e7ed69f0 r9:e7ed69f4 r8:00012e4c r7:00012e49 r6:ea8a7f54 r5:ec04dc00
    Aug 15 06:29:21 zeus kernel: [244139.356733]  r4:ef3f9c48
    Aug 15 06:29:21 zeus kernel: [244139.356740] [<c024fea8>] (alloc_extent_buffer) from [<c02224d4>] (read_tree_block+0x18/0x58)
    Aug 15 06:29:21 zeus kernel: [244139.356743]  r10:00000000 r9:e9fcfce4 r8:ec04dc00 r7:0000098c r6:00000047 r5:ec04dc00
    Aug 15 06:29:21 zeus kernel: [244139.356750]  r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356756] [<c02224bc>] (read_tree_block) from [<c0201798>] (read_block_for_search+0x11c/0x354)
    Aug 15 06:29:21 zeus kernel: [244139.356759]  r5:00000000 r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356766] [<c020167c>] (read_block_for_search) from [<c0203690>] (btrfs_search_slot+0x4a4/0x934)
    Aug 15 06:29:21 zeus kernel: [244139.356768]  r10:00000001 r9:ec04dc00 r8:e087da98 r7:00000000 r6:00000000 r5:00000001
    Aug 15 06:29:21 zeus kernel: [244139.356776]  r4:ee576f88
    Aug 15 06:29:21 zeus kernel: [244139.356782] [<c02031ec>] (btrfs_search_slot) from [<c0295d90>] (find_parent_nodes+0x204/0x85c)
    Aug 15 06:29:21 zeus kernel: [244139.356785]  r10:ee576f88 r9:00000000 r8:c06fdd0c r7:eca9a000 r6:00000000 r5:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356793]  r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356798] [<c0295b8c>] (find_parent_nodes) from [<c02964a4>] (__btrfs_find_all_roots+0xbc/0x124)
    Aug 15 06:29:21 zeus kernel: [244139.356800]  r10:00000000 r9:eca9a000 r8:00000000 r7:e9fcfe0c r6:eb72b6c0 r5:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356808]  r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356814] [<c02963e8>] (__btrfs_find_all_roots) from [<c02965b0>] (btrfs_find_all_roots+0x7c/0x8c)
    Aug 15 06:29:21 zeus kernel: [244139.356816]  r10:00000000 r9:eca9a000 r8:eca9a4fc r7:00000000 r6:eca9a000 r5:ce2f0ba0
    Aug 15 06:29:21 zeus kernel: [244139.356824]  r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356830] [<c0296534>] (btrfs_find_all_roots) from [<c029a3a8>] (btrfs_qgroup_prepare_account_extents+0x68/0xb0)
    Aug 15 06:29:21 zeus kernel: [244139.356833]  r8:ce2f0b80 r7:00000000 r6:00000000 r5:00000000 r4:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356844] [<c029a340>] (btrfs_qgroup_prepare_account_extents) from [<c022a1b4>] (btrfs_commit_transaction+0x45c/0xbd8)
    Aug 15 06:29:21 zeus kernel: [244139.356847]  r10:00000000 r9:d1426e2c r8:e9fcfed4 r7:eae4e800 r6:d14255d8 r5:ea8a7e70
    Aug 15 06:29:21 zeus kernel: [244139.356855]  r4:d1426de0
    Aug 15 06:29:21 zeus kernel: [244139.356861] [<c0229d58>] (btrfs_commit_transaction) from [<c0225258>] (transaction_kthread+0x1a8/0x218)
    Aug 15 06:29:21 zeus kernel: [244139.356863]  r10:00000000 r9:00000000 r8:0001c5da r7:e9fce000 r6:00000bb8 r5:000005c0
    Aug 15 06:29:21 zeus kernel: [244139.356871]  r4:eae4e800
    Aug 15 06:29:21 zeus kernel: [244139.356878] [<c02250b0>] (transaction_kthread) from [<c0043ce4>] (kthread+0x110/0x124)
    Aug 15 06:29:21 zeus kernel: [244139.356881]  r10:00000000 r9:00000000 r8:00000000 r7:c02250b0 r6:eae4e800 r5:00000000
    Aug 15 06:29:21 zeus kernel: [244139.356889]  r4:ea0652c0
    Aug 15 06:29:21 zeus kernel: [244139.356896] [<c0043bd4>] (kthread) from [<c0009db8>] (ret_from_fork+0x14/0x3c)
    Aug 15 06:29:21 zeus kernel: [244139.356898]  r7:00000000 r6:00000000 r5:c0043bd4 r4:ea0652c0
    Aug 15 06:29:21 zeus kernel: [244139.356904] Mem-Info:
    Aug 15 06:29:21 zeus kernel: [244139.356914] active_anon:14295 inactive_anon:9607 isolated_anon:0
    Aug 15 06:29:21 zeus kernel: [244139.356914]  active_file:9310 inactive_file:4248 isolated_file:0
    Aug 15 06:29:21 zeus kernel: [244139.356914]  unevictable:0 dirty:0 writeback:100 unstable:0
    Aug 15 06:29:21 zeus kernel: [244139.356914]  slab_reclaimable:3866 slab_unreclaimable:165956
    Aug 15 06:29:21 zeus kernel: [244139.356914]  mapped:10430 shmem:10958 pagetables:464 bounce:0
    Aug 15 06:29:21 zeus kernel: [244139.356914]  free:296657 free_pcp:388 free_cma:0
    Aug 15 06:29:21 zeus kernel: [244139.356932] Normal free:3444kB min:3484kB low:4352kB high:5224kB active_anon:14488kB inactive_anon:8088kB active_file:1856kB inactive_file:2116kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:786432kB managed:760048kB mlocked:0kB dirty:0kB writeback:400kB mapped:3420kB shmem:8844kB slab_reclaimable:15464kB slab_unreclaimable:663824kB kernel_stack:1544kB pagetables:1856kB unstable:0kB bounce:0kB free_pcp:1428kB local_pcp:736kB free_cma:0kB writeback_tmp:0kB pages_scanned:31084 all_unreclaimable? yes
    Aug 15 06:29:21 zeus kernel: [244139.356935] lowmem_reserve[]: 0 10240 10240
    Aug 15 06:29:21 zeus kernel: [244139.356950] HighMem free:1183184kB min:512kB low:2012kB high:3516kB active_anon:42692kB inactive_anon:30340kB active_file:35384kB inactive_file:14876kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:1310720kB managed:1310720kB mlocked:0kB dirty:0kB writeback:0kB mapped:38300kB shmem:34988kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB free_pcp:124kB local_pcp:120kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
    Aug 15 06:29:21 zeus kernel: [244139.356953] lowmem_reserve[]: 0 0 0
    Aug 15 06:29:21 zeus kernel: [244139.356958] Normal: 841*4kB (UME) 17*8kB (M) 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3500kB
    Aug 15 06:29:21 zeus kernel: [244139.356976] HighMem: 4858*4kB (UM) 4109*8kB (UM) 2774*16kB (UM) 1833*32kB (UM) 1460*64kB (M) 958*128kB (UM) 621*256kB (M) 389*512kB (M) 201*1024kB (M) 67*2048kB (M) 27*4096kB (M) = 1183184kB
    Aug 15 06:29:21 zeus kernel: [244139.357001] 24516 total pagecache pages
    Aug 15 06:29:21 zeus kernel: [244139.357005] 0 pages in swap cache
    Aug 15 06:29:21 zeus kernel: [244139.357008] Swap cache stats: add 0, delete 0, find 0/0
    Aug 15 06:29:21 zeus kernel: [244139.357011] Free swap  = 0kB
    Aug 15 06:29:21 zeus kernel: [244139.357013] Total swap = 0kB
    Aug 15 06:29:21 zeus kernel: [244139.357016] 524288 pages RAM
    Aug 15 06:29:21 zeus kernel: [244139.357018] 327680 pages HighMem/MovableOnly
    Aug 15 06:29:21 zeus kernel: [244139.357020] 6596 pages reserved