On Tue, Aug 6, 2019 at 3:34 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 8/5/19 5:34 PM, Pankaj Suryawanshi wrote:
> > 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)
>
> Thanks, that shows the lowmem reserve was indeed 0 for the GFP_KERNEL
allocation
> checking watermarks in the DMA zone. The zone was probably genuinely
below min
> watermark when the check happened, and things changed while the allocation
> failure was printing memory info.
Thanks Vlastimil.

lowmem reserve ? it is min_free_kbytes or something else.