Re: oom-killer

[Pankaj Suryawanshi <pankajssuryawanshi@gmail.com>]

On Mon, Aug 5, 2019 at 5:35 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 05-08-19 13:56:20, Vlastimil Babka wrote:
> > 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?


What is  lowmem_reserve[]: 0 0 579 579 ?

$cat /proc/sys/vm/lowmem_reserve_ratio
256     32      32

$cat /proc/sys/vm/min_free_kbytes
16384

here is cat /proc/zoneinfo (in normal situation not when oom)

$cat /proc/zoneinfo
Node 0, zone      DMA
  per-node stats
      nr_inactive_anon 120
      nr_active_anon 94870
      nr_inactive_file 101188
      nr_active_file 74656
      nr_unevictable 614
      nr_slab_reclaimable 12489
      nr_slab_unreclaimable 8519
      nr_isolated_anon 0
      nr_isolated_file 0
      workingset_refault 7163
      workingset_activate 7163
      workingset_nodereclaim 0
      nr_anon_pages 94953
      nr_mapped    109148
      nr_file_pages 176502
      nr_dirty     0
      nr_writeback 0
      nr_writeback_temp 0
      nr_shmem     166
      nr_shmem_hugepages 0
      nr_shmem_pmdmapped 0
      nr_anon_transparent_hugepages 0
      nr_unstable  0
      nr_vmscan_write 0
      nr_vmscan_immediate_reclaim 0
      nr_dirtied   7701
      nr_written   6978
  pages free     49492
        min      4096
        low      6416
        high     7440
        spanned  131072
        present  114688
        managed  105724
        protection: (0, 0, 1491, 1491)
      nr_free_pages 49492
      nr_zone_inactive_anon 0
      nr_zone_active_anon 0
      nr_zone_inactive_file 65
      nr_zone_active_file 4859
      nr_zone_unevictable 0
      nr_zone_write_pending 0
      nr_mlock     0
      nr_page_table_pages 4352
      nr_kernel_stack 9056
      nr_bounce    0
      nr_zspages   0
      nr_free_cma  0
  pagesets
    cpu: 0
              count: 16
              high:  186
              batch: 31
  vm stats threshold: 18
    cpu: 1
              count: 138
              high:  186
              batch: 31
  vm stats threshold: 18
    cpu: 2
              count: 156
              high:  186
              batch: 31
  vm stats threshold: 18
    cpu: 3
              count: 170
              high:  186
              batch: 31
  vm stats threshold: 18
  node_unreclaimable:  0
  start_pfn:           131072
  node_inactive_ratio: 0
Node 0, zone   Normal
  pages free     0
        min      0
        low      0
        high     0
        spanned  0
        present  0
        managed  0
        protection: (0, 0, 11928, 11928)
Node 0, zone  HighMem
  pages free     63096
        min      128
        low      8506
        high     12202
        spanned  393216
        present  381696
        managed  381696
        protection: (0, 0, 0, 0)
      nr_free_pages 63096
      nr_zone_inactive_anon 120
      nr_zone_active_anon 94863
      nr_zone_inactive_file 101123
      nr_zone_active_file 69797
      nr_zone_unevictable 614
      nr_zone_write_pending 0
      nr_mlock     614
      nr_page_table_pages 1478
      nr_kernel_stack 0
      nr_bounce    0
      nr_zspages   0
      nr_free_cma  62429
  pagesets
    cpu: 0
              count: 30
              high:  186
              batch: 31
  vm stats threshold: 30
    cpu: 1
              count: 13
              high:  186
              batch: 31
  vm stats threshold: 30
    cpu: 2
              count: 9
              high:  186
              batch: 31
  vm stats threshold: 30
    cpu: 3
              count: 46
              high:  186
              batch: 31
  vm stats threshold: 30
  node_unreclaimable:  0
  start_pfn:           262144
  node_inactive_ratio: 0
Node 0, zone  Movable
  pages free     0
        min      32
        low      32
        high     32
        spanned  0
        present  0
        managed  0
        protection: (0, 0, 0, 0)
>
>
> This is GFP_KERNEL request essentially so there shouldn't be any lowmem
> reserve here, no?


Why only low 1G is accessible by kernel in 32-bit system ?


My system configuration is :-
3G/1G - vmsplit
vmalloc = 480M (I think vmalloc size will set your highmem ?)

here is my memory layout :-
[    0.000000] Virtual kernel memory layout:
[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
[    0.000000]     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
[    0.000000]     vmalloc : 0xe0800000 - 0xff800000   ( 496 MB)
[    0.000000]     lowmem  : 0xc0000000 - 0xe0000000   ( 512 MB)
[    0.000000]     pkmap   : 0xbfe00000 - 0xc0000000   (   2 MB)
[    0.000000]     modules : 0xbf000000 - 0xbfe00000   (  14 MB)
[    0.000000]       .text : 0xc0008000 - 0xc0c00000   (12256 kB)
[    0.000000]       .init : 0xc1000000 - 0xc1200000   (2048 kB)
[    0.000000]       .data : 0xc1200000 - 0xc143c760   (2290 kB)
[    0.000000]        .bss : 0xc1447840 - 0xc14c3ad4   ( 497 kB)
>
> --
> Michal Hocko
> SUSE Labs