What could cause out_of_memory & __alloc_pages

Question

Sadly my server is permanently hangging due to out of memory:

Nov  8 07:30:43 crawler kernel:
Nov  8 07:30:43 crawler kernel: Call Trace:
Nov  8 07:30:43 crawler kernel:  [<ffffffff800cb625>] out_of_memory+0x8e/0x2f3
Nov  8 07:30:43 crawler kernel:  [<ffffffff8000f691>] __alloc_pages+0x27f/0x308
Nov  8 07:30:43 crawler kernel:  [<ffffffff80013074>] __do_page_cache_readahead+0x96/0x17b
Nov  8 07:30:43 crawler kernel:  [<ffffffff800139b5>] filemap_nopage+0x14c/0x360
Nov  8 07:30:43 crawler kernel:  [<ffffffff80008972>] __handle_mm_fault+0x1fd/0x103b
Nov  8 07:30:43 crawler kernel:  [<ffffffff8003ddfb>] lock_timer_base+0x1b/0x3c
Nov  8 07:30:43 crawler kernel:  [<ffffffff800671ae>] do_page_fault+0x499/0x842
Nov  8 07:30:43 crawler kernel:  [<ffffffff800638a7>] schedule_timeout+0x92/0xad
Nov  8 07:30:43 crawler kernel:  [<ffffffff8009aa88>] process_timeout+0x0/0x5
Nov  8 07:30:43 crawler kernel:  [<ffffffff800ff108>] sys_epoll_wait+0x42f/0x475
Nov  8 07:30:46 crawler kernel:  [<ffffffff8008f4a9>] default_wake_function+0x0/0xe
Nov  8 07:30:46 crawler kernel:  [<ffffffff8005ddf9>] error_exit+0x0/0x84
Nov  8 07:30:46 crawler kernel:
Nov  8 07:30:46 crawler kernel: Mem-info:
Nov  8 07:30:47 crawler kernel: Node 0 DMA per-cpu:
Nov  8 07:30:47 crawler kernel: cpu 0 hot: high 0, batch 1 used:0
Nov  8 07:30:47 crawler kernel: cpu 0 cold: high 0, batch 1 used:0
Nov  8 07:30:47 crawler kernel: cpu 1 hot: high 0, batch 1 used:0
Nov  8 07:30:47 crawler kernel: cpu 1 cold: high 0, batch 1 used:0
Nov  8 07:30:47 crawler kernel: Node 0 DMA32 per-cpu:
Nov  8 07:30:47 crawler kernel: cpu 0 hot: high 186, batch 31 used:27
Nov  8 07:30:47 crawler kernel: cpu 0 cold: high 62, batch 15 used:58
Nov  8 07:30:47 crawler kernel: cpu 1 hot: high 186, batch 31 used:62
Nov  8 07:30:47 crawler kernel: cpu 1 cold: high 62, batch 15 used:40
Nov  8 07:30:47 crawler kernel: Node 0 Normal per-cpu:
Nov  8 07:30:47 crawler kernel: cpu 0 hot: high 186, batch 31 used:124
Nov  8 07:30:48 crawler kernel: cpu 0 cold: high 62, batch 15 used:47
Nov  8 07:30:48 crawler kernel: cpu 1 hot: high 186, batch 31 used:32
Nov  8 07:30:48 crawler kernel: cpu 1 cold: high 62, batch 15 used:59
Nov  8 07:30:48 crawler kernel: Node 0 HighMem per-cpu: empty
Nov  8 07:30:48 crawler kernel: Free pages:       19904kB (0kB HighMem)
Nov  8 07:30:48 crawler kernel: Active:539752 inactive:442402 dirty:0 writeback:0 unstable:0 free:4976 slab:4557 mapped-file:1157 mapped-anon:981453 pagetables:14118
Nov  8 07:30:48 crawler kernel: Node 0 DMA free:10072kB min:16kB low:20kB high:24kB active:0kB inactive:0kB present:9676kB pages_scanned:0 all_unreclaimable? yes
Nov  8 07:30:48 crawler kernel: lowmem_reserve[]: 0 3511 4016 4016

http://pastebin.com/tySD9g5W

Answer 1

This occurs when your system memory is completely exhausted. System can no longer allocate space for any new variables as your physical memory and swap has been completely used up. The main reason for this is improper memory management in applications.