Re: OOM Killer firing when plenty of memory left and no swap used

[Mike Galbraith]

On Thu, 2006-05-11 at 12:08 +1000, Bron Gondwana wrote:
> 
> I hope someone can shed some light on what could possibly
> have caused the oom-killer to engage with so much free
> memory.

> Log messages from the first failure:
> May 10 19:57:00 heartbeat1 kernel: oom-killer: gfp_mask=0xd0, order=1

A two page GFP_KERNEL allocation fails...

> May 10 19:57:00 heartbeat1 kernel:  [out_of_memory+180/209] out_of_memory+0xb4/0xd1
> May 10 19:57:00 heartbeat1 kernel:  [__alloc_pages+623/795] __alloc_pages+0x26f/0x31boom-killer: gfp_mask=0xd0, order=1
> May 10 19:57:00 heartbeat1 kernel:  [out_of_memory+180/209] out_of_memory+0xb4/0xd1
> May 10 19:57:00 heartbeat1 kernel:  [__alloc_pages+623/795] __alloc_pages+0x26f/0x31b
> May 10 19:57:00 heartbeat1 kernel:  [kmem_getpages+52/155] kmem_getpages+0x34/0x9b
> May 10 19:57:00 heartbeat1 kernel:  [cache_grow+190/375] cache_grow+0xbe/0x177
> May 10 19:57:00 heartbeat1 kernel:  [cache_alloc_refill+354/523] cache_alloc_refill+0x162/0x20b
> May 10 19:57:00 heartbeat1 kernel:  [kmem_cache_alloc+103/127] kmem_cache_alloc+0x67/0x7f
> May 10 19:57:00 heartbeat1 kernel:  [dup_task_struct+69/153] dup_task_struct+0x45/0x99
> May 10 19:57:00 heartbeat1 kernel:  [copy_process+94/3348] copy_process+0x5e/0xd14
> May 10 19:57:00 heartbeat1 kernel:  [do_fork+105/395] do_fork+0x69/0x18b
> May 10 19:57:00 heartbeat1 kernel:  [sys_rt_sigprocmask+161/256] sys_rt_sigprocmask+0xa1/0x100
> May 10 19:57:00 heartbeat1 kernel:  [sys_clone+62/66] sys_clone+0x3e/0x42
> May 10 19:57:00 heartbeat1 kernel:  [syscall_call+7/11] syscall_call+0x7/0xb

...for the slab allocator as it tries to expand it's cache to create
space for a new task. 

> May 10 19:57:00 heartbeat1 kernel: Normal free:24276kB min:26732kB low:33412kB high:40096kB active:2256kB inactive:1940kB present:901120kB pages_scanned:6457 all_unreclaimable? yes

Zone normal is below min watermark, and GFP_HIGH isn't set, so no
digging down into reserves is allowed.  Most of Zone Normal memory isn't
on the LRU, and what is there is all unreclaimable, so swap can't help
with the shortage.  Genuine oom situation.

Question is, where are all your Zone Normal pages hanging out?  If it
happens again, take a look at /proc/slabinfo to see if it's there, and
if so, in which cache[s].

If it's not there, somebody is leaking pages.  If that's the case, I'd
take a close look at those out-of-tree patches.

	-Mike

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