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I am running an Amazon AWS Micro Linux Instance and it crashed during some "light" usage a few days ago. I am running an app that uploads photos to the server. We had maybe 10 users uploading multiple photos during a 1 hour period.

At some point, the server stopped responding. I logged into the AWS Console and found that the "Intstance Reachability Check" had failed. I rebooted the server, restarted PHP and MySQL, and then had to repair a few MySQL tables that had been corrupted.

I had the monitoring tools turned on and the CPU Usage indicates that we topped out at 28% CPU Usage - After reading some more documentation about Micro Instances, I do not think we maxed out on the CPU, but I could be wrong.

I don't know a enough to understand what the logs mean. I have found what I believe to be the logs from the server from the time where the problem occurred, I am hoping that someone can help me decipher what happened:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157082] httpd invoked oom-killer: gfp_mask=0x201da, order=0, oom_adj=0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157100] httpd cpuset=/ mems_allowed=0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157108] Pid: 1824, comm: httpd Not tainted 2.6.35.14-97.44.amzn1.x86_64 #1

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157117] Call Trace:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157131] [] ? cpuset_print_task_mems_allowed+0x98/0xa0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157143] [] dump_header.clone.1+0x77/0x1a0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157153] [] ? _raw_spin_unlock_irqrestore+0x19/0x20

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157164] [] ? ___ratelimit+0x9f/0x120

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157172] [] oom_kill_process.clone.0+0x76/0x140

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157185] [] __out_of_memory+0x118/0x190

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157196] [] out_of_memory+0x82/0x1c0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157204] [] __alloc_pages_nodemask+0x689/0x6a0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157215] [] alloc_pages_current+0x94/0xf0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157223] [] __page_cache_alloc+0x7f/0x90

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157232] [] __do_page_cache_readahead+0xc0/0x200

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157240] [] ra_submit+0x1c/0x20

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157248] [] filemap_fault+0x3e3/0x430

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157257] [] __do_fault+0x4f/0x4b0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157265] [] handle_mm_fault+0x1b4/0xb40

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157275] [] ? xen_clocksource_read+0x21/0x30

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157283] [] ? xen_clocksource_get_cycles+0x9/0x10

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157293] [] ? ktime_get_ts+0xa3/0xd0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157302] [] do_page_fault+0x112/0x310

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157310] [] page_fault+0x25/0x30

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157316] Mem-Info:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157320] Node 0 DMA per-cpu:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157327] CPU 0: hi: 0, btch: 1 usd: 0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157332] Node 0 DMA32 per-cpu:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157339] CPU 0: hi: 186, btch: 31 usd: 30Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157347] active_anon:70901 inactive_anon:71000 isolated_anon:0Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157348] active_file:13 inactive_file:28 isolated_file:0Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157349] unevictable:0 dirty:4 writeback:0 unstable:0Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157350] free:1374 slab_reclaimable:613 slab_unreclaimable:1843

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157351] mapped:25 shmem:34 pagetables:4842 bounce:0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157430] Node 0 DMA free:2436kB min:76kB low:92kB high:112kB active_anon:6104kB inactive_anon:6272kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15772kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:20kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157459] lowmem_reserve[]: 0 590 590 590

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157475] Node 0 DMA32 free:3060kB min:3068kB low:3832kB high:4600kB active_anon:277500kB inactive_anon:277728kB active_file:52kB inactive_file:112kB unevictable:0kB isolated(anon):0k B isolated(file):0kB present:604988kB mlocked:0kB dirty:16kB writeback:0kB mapped:100kB shmem:136kB slab_reclaimable:2452kB slab_unreclaimable:7372kB kernel_stack:752kB pagetables:19348kB unstable:0kB bounce:0kB writeback_tmp:0kB pa ges_scanned:256 all_unreclaimable? yes

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157503] lowmem_reserve[]: 0 0 0 0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157518] Node 0 DMA: 1*4kB 0*8kB 0*16kB 0*32kB 0*64kB 1*128kB 1*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 2436kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157553] Node 0 DMA32: 729*4kB 4*8kB 5*16kB 1*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3060kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157587] 80 total pagecache pages

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157592] 0 pages in swap cache

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157597] Swap cache stats: add 0, delete 0, find 0/0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157602] Free swap = 0kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.157607] Total swap = 0kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] 157439 pages RAM

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] 4626 pages reserved

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] 38855 pages shared

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] 149663 pages non-shared

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] Out of memory: kill process 2135 (httpd) score 87500 or a child

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.158050] Killed process 2135 (httpd) vsz:350000kB, anon-rss:49376kB, file-rss:0kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.164960] httpd invoked oom-killer: gfp_mask=0x201da, order=0, oom_adj=0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.164990] httpd cpuset=/ mems_allowed=0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.164998] Pid: 1824, comm: httpd Not tainted 2.6.35.14-97.44.amzn1.x86_64 #1

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165006] Call Trace:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165020] [] ? cpuset_print_task_mems_allowed+0x98/0xa0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165032] [] dump_header.clone.1+0x77/0x1a0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165042] [] ? _raw_spin_unlock_irqrestore+0x19/0x20

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165053] [] ? ___ratelimit+0x9f/0x120

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165061] [] oom_kill_process.clone.0+0x76/0x140

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165069] [] __out_of_memory+0x118/0x190

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165077] [] out_of_memory+0x82/0x1c0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165086] [] __alloc_pages_nodemask+0x689/0x6a0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165096] [] alloc_pages_current+0x94/0xf0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165105] [] __page_cache_alloc+0x7f/0x90

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165114] [] __do_page_cache_readahead+0xc0/0x200

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165122] [] ra_submit+0x1c/0x20

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165129] [] filemap_fault+0x3e3/0x430

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165139] [] __do_fault+0x4f/0x4b0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165147] [] handle_mm_fault+0x1b4/0xb40

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165156] [] ? xen_clocksource_read+0x21/0x30

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165164] [] ? xen_clocksource_get_cycles+0x9/0x10

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165178] [] ? ktime_get_ts+0xa3/0xd0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165187] [] do_page_fault+0x112/0x310

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165195] [] page_fault+0x25/0x30

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165201] Mem-Info:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165205] Node 0 DMA per-cpu:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165212] CPU 0: hi: 0, btch: 1 usd: 0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165217] Node 0 DMA32 per-cpu:

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165224] CPU 0: hi: 186, btch: 31 usd: 130

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165232] active_anon:70836 inactive_anon:71000 isolated_anon:0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165233] active_file:13 inactive_file:28 isolated_file:0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165234] unevictable:0 dirty:4 writeback:0 unstable:0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165235] free:1343 slab_reclaimable:613 slab_unreclaimable:1843

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165236] mapped:25 shmem:34 pagetables:4842 bounce:0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165262] Node 0 DMA free:2436kB min:76kB low:92kB high:112kB active_anon:6104kB inactive_anon:6272kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15772kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:20kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165290] lowmem_reserve[]: 0 590 590 590

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165305] Node 0 DMA32 free:2936kB min:3068kB low:3832kB high:4600kB active_anon:277240kB inactive_anon:277728kB active_file:52kB inactive_file:112kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:604988kB mlocked:0kB dirty:16kB writeback:0kB mapped:100kB shmem:136kB slab_reclaimable:2452kB slab_unreclaimable:7372kB kernel_stack:752kB pagetables:19348kB unstable:0kB bounce:0kB writeback_tmp:0kB pa ges_scanned:256 all_unreclaimable? yes

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165334] lowmem_reserve[]: 0 0 0 0Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165348] Node 0 DMA: 1*4kB 0*8kB 0*16kB 0*32kB 0*64kB 1*128kB 1*25 6kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 2436kBJul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165420] Node 0 DMA32: 710*4kB 4*8kB 4*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 2936kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 80 total pagecache pages

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 0 pages in swap cache

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Swap cache stats: add 0, delete 0, find 0/0

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Free swap = 0kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Total swap = 0kB

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 157439 pages RAM

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 4626 pages reserved

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 37922 pages shared

Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] 149594 pages non-sharedJul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Out of memory: kill process 1859 (httpd) score 87366 or a childJul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Killed process 1859 (httpd) vsz:349464kB, anon-rss:49312k B, file-rss:0kB

Please let me know if there is anything additional that I can provide.

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1  
Do you even bother to read the logs? Jul 23 00:19:07 ip-10-117-66-219 kernel: [19699669.165290] lowmem_reserve[]: 0 590 590 590 00:19:07 ip-10-117-66-219 kernel: [19699669.165648] Out of memory: kill process 1859 (httpd) score 87366 or a child ` –  bwight Jul 24 '12 at 21:36
    
I see several references to running out of memory. When that happens GNU/Linux starts killing random processes. (I never figured out why this was better than just returning OOM). –  Hennes Jul 24 '12 at 21:37
    
Possible duplicate: serverfault.com/questions/134669/… –  Michael Hampton Jul 24 '12 at 21:44

2 Answers 2

up vote 2 down vote accepted

The Linux out-of-memory killer felt obliged to free some RAM. Which it then attempted to do (httpd being the logged target). However, it looks like it was not successful enough and ended up locking up hard, which would not get logged since the server was out of RAM and thus didn't have memory for log-buffers.

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So given the information here, I would need to upgrade to a server with more RAM. Whenever it talks about "Memory" I do not know if it is referencing RAM or disk space. Thank You. –  Chris Jul 24 '12 at 21:56
2  
You've got two options: You can tune your server processes to use less RAM (apache in particular in its default configuration can use more RAM than you have) or upgrade to a larger EC2 instance. –  Michael Hampton Jul 24 '12 at 22:01

You're out of memory. It's a small instance that doesn't have enough RAM to support your application. You're a victim of the OOM Killer.

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