Re: oom-killer

From: Pankaj Suryawanshi
Date: Mon Aug 05 2019 - 11:35:05 EST

On Mon, Aug 5, 2019 at 5:35 PM Michal Hocko <mhocko@xxxxxxxxxx> 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