Re: Out of memory error

Re: Out of memory error

[Peter Zijlstra]

On Sat, 2009-01-31 at 21:17 +0800, Cliffe wrote:
> Hello,
> 
> I get the following error messages from code I am working on. It works 
> fine in userspace.

its very very unlikely you'll ever experience malloc() failing in
userspace.

> I suspect it may be due to the kernel's limited stack size as it uses a 
> recursive algorithm. If this is the cause, how can I provide the (lsm) 
> module with more memory?

You cannot, you'll have to rewrite your code to be iterative and use an
allocated traversal stack.

>  This is for a research project so it is ok if 
> the solution is not quite kosher.

And here you shatter my illusion that science is careful work ;-)

> Thank you, any help will be appreciated. Please CC me in on any replies.

Its simply a case of you using kmalloc(GFP_ATOMIC) and that's failing.
Furthermore, it appears to me you're not using frame pointers for your
kernel builds, please ammend that, it gives far more readable output.

> The following is only an harmless informational message.
> Unless you get a _continuous_flood_ of these messages it means
> everything is working fine. Allocations from irqs cannot be
> perfectly reliable and the kernel is designed to handle that.
> bash: page allocation failure. order:0, mode:0x20
>  [<c015846a>] __alloc_pages+0x2c5/0x2d6
>  [<c016de72>] cache_alloc_refill+0x2ae/0x4c1
>  [<c0129640>] irq_exit+0x53/0x6b
>  [<c016e0fc>] __kmalloc+0x77/0x8f
>  [<e1060c01>] mem_alloc+0x19/0x5f [fbac_lsm]
>  [<e1069b14>] copy_to_new_to_send_recursive+0x22/0x91 [fbac_lsm]
>  [<e1069cf3>] copy_to_new_func_recursive+0xde/0x11d [fbac_lsm]
>  [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
>  [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
>  [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
>  [<e10633fc>] build_task_tree_found_application+0x82/0x144 [fbac_lsm]
>  [<e10635d7>] build_task_tree_find_application+0x9d/0x1a5 [fbac_lsm]
>  [<e106381c>] build_task_tree+0x13d/0x1a1 [fbac_lsm]
>  [<e1064ca9>] start_task+0x32/0x175 [fbac_lsm]
>  [<e1060a6a>] fbac_lsm_bprm_set_security+0x124/0x1f1 [fbac_lsm]
>  [<c017449f>] prepare_binprm+0xa7/0xd0
>  [<c0173f27>] count+0x14/0x3f
>  [<c017597f>] do_execve+0xef/0x1e1
>  [<c01036fe>] sys_execve+0x2f/0x78
>  [<c0104e22>] sysenter_past_esp+0x6b/0xa9
>  =======================
> Mem-info:
> DMA per-cpu:
> CPU    0: Hot: hi:    0, btch:   1 usd:   0   Cold: hi:    0, btch:   1 
> usd:   0
> Normal per-cpu:
> CPU    0: Hot: hi:  186, btch:  31 usd:  22   Cold: hi:   62, btch:  15 
> usd:  12
> Active:50484 inactive:64525 dirty:108 writeback:0 unstable:0
>  free:761 slab:10659 mapped:10607 pagetables:421 bounce:0
> DMA free:2000kB min:88kB low:108kB high:132kB active:392kB 
> inactive:8332kB present:16256kB pages_scanned:0 all_unreclaimable? no
> lowmem_reserve[]: 0 492 492
> Normal free:1044kB min:2792kB low:3488kB high:4188kB active:201544kB 
> inactive:249768kB present:503936kB pages_scanned:0 all_unreclaimable? no
> lowmem_reserve[]: 0 0 0
> DMA: 0*4kB 0*8kB 1*16kB 0*32kB 1*64kB 1*128kB 1*256kB 1*512kB 1*1024kB 
> 0*2048kB 0*4096kB = 2000kB
> Normal: 1*4kB 0*8kB 1*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 
> 1*1024kB 0*2048kB 0*4096kB = 1044kB
> Swap cache: add 0, delete 0, find 0/0, race 0+0
> Free swap  = 0kB
> Total swap = 0kB
> Free swap:            0kB
> 131072 pages of RAM
> 0 pages of HIGHMEM
> 2092 reserved pages
> 92964 pages shared
> 0 pages swap cached
> 108 pages dirty
> 0 pages writeback
> 10607 pages mapped
> 10659 pages slab
> 421 pages pagetables
> 
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Out of memory error

[Cliffe]

Hello,

I get the following error messages from code I am working on. It works 
fine in userspace.

I suspect it may be due to the kernel's limited stack size as it uses a 
recursive algorithm. If this is the cause, how can I provide the (lsm) 
module with more memory? This is for a research project so it is ok if 
the solution is not quite kosher.

Thank you, any help will be appreciated. Please CC me in on any replies.

Cliffe.

The message:

The following is only an harmless informational message.
Unless you get a _continuous_flood_ of these messages it means
everything is working fine. Allocations from irqs cannot be
perfectly reliable and the kernel is designed to handle that.
bash: page allocation failure. order:0, mode:0x20
 [<c015846a>] __alloc_pages+0x2c5/0x2d6
 [<c016de72>] cache_alloc_refill+0x2ae/0x4c1
 [<c0129640>] irq_exit+0x53/0x6b
 [<c016e0fc>] __kmalloc+0x77/0x8f
 [<e1060c01>] mem_alloc+0x19/0x5f [fbac_lsm]
 [<e1069b14>] copy_to_new_to_send_recursive+0x22/0x91 [fbac_lsm]
 [<e1069cf3>] copy_to_new_func_recursive+0xde/0x11d [fbac_lsm]
 [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
 [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
 [<e1069ce3>] copy_to_new_func_recursive+0xce/0x11d [fbac_lsm]
 [<e10633fc>] build_task_tree_found_application+0x82/0x144 [fbac_lsm]
 [<e10635d7>] build_task_tree_find_application+0x9d/0x1a5 [fbac_lsm]
 [<e106381c>] build_task_tree+0x13d/0x1a1 [fbac_lsm]
 [<e1064ca9>] start_task+0x32/0x175 [fbac_lsm]
 [<e1060a6a>] fbac_lsm_bprm_set_security+0x124/0x1f1 [fbac_lsm]
 [<c017449f>] prepare_binprm+0xa7/0xd0
 [<c0173f27>] count+0x14/0x3f
 [<c017597f>] do_execve+0xef/0x1e1
 [<c01036fe>] sys_execve+0x2f/0x78
 [<c0104e22>] sysenter_past_esp+0x6b/0xa9
 =======================
Mem-info:
DMA per-cpu:
CPU    0: Hot: hi:    0, btch:   1 usd:   0   Cold: hi:    0, btch:   1 
usd:   0
Normal per-cpu:
CPU    0: Hot: hi:  186, btch:  31 usd:  22   Cold: hi:   62, btch:  15 
usd:  12
Active:50484 inactive:64525 dirty:108 writeback:0 unstable:0
 free:761 slab:10659 mapped:10607 pagetables:421 bounce:0
DMA free:2000kB min:88kB low:108kB high:132kB active:392kB 
inactive:8332kB present:16256kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 492 492
Normal free:1044kB min:2792kB low:3488kB high:4188kB active:201544kB 
inactive:249768kB present:503936kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0
DMA: 0*4kB 0*8kB 1*16kB 0*32kB 1*64kB 1*128kB 1*256kB 1*512kB 1*1024kB 
0*2048kB 0*4096kB = 2000kB
Normal: 1*4kB 0*8kB 1*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 
1*1024kB 0*2048kB 0*4096kB = 1044kB
Swap cache: add 0, delete 0, find 0/0, race 0+0
Free swap  = 0kB
Total swap = 0kB
Free swap:            0kB
131072 pages of RAM
0 pages of HIGHMEM
2092 reserved pages
92964 pages shared
0 pages swap cached
108 pages dirty
0 pages writeback
10607 pages mapped
10659 pages slab
421 pages pagetables

Re: Out of memory error

[Peter Zijlstra]

On Sat, 2009-01-31 at 22:30 +0800, Cliffe wrote:

> > Its simply a case of you using kmalloc(GFP_ATOMIC) and that's failing.
> >   
> 
> So it has nothing to do with stack size because we are talking heap?
> What could be causing the problem?

Right, heap. The thing is, Linux has a greedy memory usage, and tries to
keep as much as possible in memory, this means that we're basically in a
constant state of low memory.

Regular allocations (GFP_KERNEL) can sleep, and can therefore reclaim
memory (write out stuff dirty to disk, swap a little, etc..).

Your allocation (GFP_ATOMIC) isn't allowed to sleep, and can therefore
not reclaim memory -- if it really hits rock bottom, not uncommon, it
just fails to provide memory.

Any code using GFP_ATOMIC (or for that matter, any kernel allocation,
GFP_KERNEL can fail too, just not as easy) must be able to deal with
allocation failures.

How to do that is very domain specific.

> How limited is the stack?

Depends on the arch and build details, 4k is a reasonable assumption.

> > Furthermore, it appears to me you're not using frame pointers for your
> > kernel builds, please ammend that, it gives far more readable output.
> >   
> 
> I'll look into that. Is that a kernel compile config option?

CONFIG_FRAME_POINTER=y