Re: 2.6.39-rc4+: oom-killer busy killing tasks

[Minchan Kim]

On Fri, Apr 22, 2011 at 10:57 AM, Christian Kujau <lists@xxxxxxxxxxxxxxx> wrote:
> Hi,
>
> after the block layer regression[0] seemed to be fixed, the machine
> appeared to be running fine. But after putting some disk I/O to the system
> (PowerBook G4) it became unresponsive, I/O wait went up high and I could
> see that the OOM killer was killing processes. Logging in via SSH was
> sometimes possible, but the each session was killed shortly after, so I
> could not do much.
>
> The box finally rebooted itself, the logfile recorded something xfs
> related in the first backtrace, hence I'm cc'ing the xfs list too:
>
> du invoked oom-killer: gfp_mask=0x842d0, order=0, oom_adj=0, oom_score_adj=0
> Call Trace:
> [c0009ce4] show_stack+0x70/0x1bc (unreliable)
> [c008f508] T.528+0x74/0x1cc
> [c008f734] T.526+0xd4/0x2a0
> [c008fb7c] out_of_memory+0x27c/0x360
> [c0093b3c] __alloc_pages_nodemask+0x6f8/0x708
> [c00c00b4] new_slab+0x244/0x27c
> [c00c0620] T.879+0x1cc/0x37c
> [c00c08d0] kmem_cache_alloc+0x100/0x108
> [c01cb2b8] kmem_zone_alloc+0xa4/0x114
> [c01a7d58] xfs_inode_alloc+0x40/0x13c
> [c01a8218] xfs_iget+0x258/0x5a0
> [c01c922c] xfs_lookup+0xf8/0x114
> [c01d70b0] xfs_vn_lookup+0x5c/0xb0
> [c00d14c8] d_alloc_and_lookup+0x54/0x90
> [c00d1d4c] do_lookup+0x248/0x2bc
> [c00d33cc] path_lookupat+0xfc/0x8f4
> [c00d3bf8] do_path_lookup+0x34/0xac
> [c00d53e0] user_path_at+0x64/0xb4
> [c00ca638] vfs_fstatat+0x58/0xbc
> [c00ca6c0] sys_fstatat64+0x24/0x50
> [c00124f4] ret_from_syscall+0x0/0x38
> Â--- Exception: c01 at 0xff4b050
> Â LR = 0x10008cf8
>
>
> This is wih today's git (91e8549bde...); full log & .config on:
>
> Âhttp://nerdbynature.de/bits/2.6.39-rc4/oom/

You would try to allocate a page from DMA as you don't have a normal zone.

Although free pages in DMA zone is about 3M, free pages of zone is
below min of DMA zone. So zone_watermark_ok would be failed.

But I wonder why VM can't reclaim the pages. As I see the log, there
are lots of slab pages(710M) in DMA zone while LRU pages are very
small. SLAB pages are things VM has a trouble to reclaim. I am not
sure 710M of SLAB is reasonable size. Don't you have experience same
problem in old kernel?
If you see the problem first in 2.6.39-rc4, maybe it would be a
regression(ex, might be slab memory leak)
Could you get the information about slabinfo(ex, cat /proc/slabinfo)
right before OOM happens.
It could say culprit.

-- 
Kind regards,
Minchan Kim
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