Re: oom-killer

[Vlastimil Babka]

On 8/5/19 1:24 PM, Michal Hocko wrote:
>> [  727.954355] CPU: 0 PID: 56 Comm: kworker/u8:2 Tainted: P           O  4.14.65 #606
> [...]
>> [  728.029390] [<c034a094>] (oom_kill_process) from [<c034af24>] (out_of_memory+0x140/0x368)
>> [  728.037569]  r10:00000001 r9:c12169bc r8:00000041 r7:c121e680 r6:c1216588 r5:dd347d7c > [  728.045392]  r4:d5737080
>> [  728.047929] [<c034ade4>] (out_of_memory) from [<c03519ac>]  (__alloc_pages_nodemask+0x1178/0x124c)
>> [  728.056798]  r7:c141e7d0 r6:c12166a4 r5:00000000 r4:00001155
>> [  728.062460] [<c0350834>] (__alloc_pages_nodemask) from [<c021e9d4>] (copy_process.part.5+0x114/0x1a28)
>> [  728.071764]  r10:00000000 r9:dd358000 r8:00000000 r7:c1447e08 r6:c1216588 r5:00808111
>> [  728.079587]  r4:d1063c00
>> [  728.082119] [<c021e8c0>] (copy_process.part.5) from [<c0220470>] (_do_fork+0xd0/0x464)
>> [  728.090034]  r10:00000000 r9:00000000 r8:dd008400 r7:00000000 r6:c1216588 r5:d2d58ac0
>> [  728.097857]  r4:00808111
> 
> The call trace tells that this is a fork (of a usermodhlper but that is
> not all that important.
> [...]
>> [  728.260031] DMA free:17960kB min:16384kB low:25664kB high:29760kB active_anon:3556kB inactive_anon:0kB active_file:280kB inactive_file:28kB unevictable:0kB writepending:0kB present:458752kB managed:422896kB mlocked:0kB kernel_stack:6496kB pagetables:9904kB bounce:0kB free_pcp:348kB local_pcp:0kB free_cma:0kB
>> [  728.287402] lowmem_reserve[]: 0 0 579 579
> 
> So this is the only usable zone and you are close to the min watermark
> which means that your system is under a serious memory pressure but not
> yet under OOM for order-0 request. The situation is not great though

Looking at lowmem_reserve above, wonder if 579 applies here? What does
/proc/zoneinfo say?

> because there is close to no reclaimable memory (look at *_anon, *_file)
> counters and it is quite likely that compaction will stubmle over
> unmovable pages very often as well.
> 
>> [  728.326634] DMA: 71*4kB (EH) 113*8kB (UH) 207*16kB (UMH) 103*32kB (UMH) 70*64kB (UMH) 27*128kB (UMH) 5*256kB (UMH) 1*512kB (H) 0*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB = 17524kB
> 
> This is more interesting because there seem to be order-1+ blocks to
> be used for this allocation. H stands for High atomic reserve, U for
> unmovable blocks and GFP_KERNEL belong to such an allocation and M is
> for movable pageblock (see show_migration_types for all migration
> types). From the above it would mean that the allocation should pass
> through but note that the information is dumped after the last watermark
> check so the situation might have changed.
> 
> In any case your system seems to be tight on the lowmem and I would
> expect it could get to OOM in peak memory demand on top of the current
> state.
>