linux-kernel - Re: Still OOM problems with 4.9er/4.10er kernels

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Date:   Mon, 27 Feb 2017 09:27:35 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Gerhard Wiesinger <lists@...singer.com>
Cc:     Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Still OOM problems with 4.9er/4.10er kernels

On Sun 26-02-17 09:40:42, Gerhard Wiesinger wrote:
> On 04.01.2017 10:11, Michal Hocko wrote:
> >>The VM stops working (e.g. not pingable) after around 8h (will be restarted
> >>automatically), happened serveral times.
> >>
> >>Had also further OOMs which I sent to Mincham.
> >Could you post them to the mailing list as well, please?
> 
> Still OOMs on dnf update procedure with kernel 4.10: 4.10.0-1.fc26.x86_64 as
> well on 4.9.9-200.fc25.x86_64
> 
> On 4.10er kernels:
[...]
> kernel: Node 0 DMA32 free:5012kB min:2264kB low:2828kB high:3392kB
> active_anon:143580kB inactive_anon:143300kB active_file:2576kB
> inactive_file:2560kB unevictable:0kB writepending:0kB present:376688kB
> managed:353968kB mlocked:0kB slab_reclaimable:13708kB
> slab_unreclaimable:18064kB kernel_stack:2352kB pagetables:12888kB bounce:0kB
> free_pcp:412kB local_pcp:88kB free_cma:0kB
[...]

> On 4.9er kernels:
[...]
> kernel: Node 0 DMA32 free:3356kB min:2668kB low:3332kB high:3996kB
> active_anon:122148kB inactive_anon:112068kB active_file:81324kB
> inactive_file:101972kB unevictable:0kB writepending:4648kB present:507760kB
> managed:484384kB mlocked:0kB slab_reclaimable:17660kB
> slab_unreclaimable:21404kB kernel_stack:2432kB pagetables:10124kB bounce:0kB
> free_pcp:120kB local_pcp:0kB free_cma:0kB

In both cases the amount if free memory is above the min watermark, so
we shouldn't be hitting the oom. We might have somebody freeing memory
after the last attempt, though...

[...]
> Should be very easy to reproduce with a low mem VM (e.g. 192MB) under KVM
> with ext4 and Fedora 25 and some memory load and updating the VM.
> 
> Any further progress?

The linux-next (resp. mmotm tree) has new tracepoints which should help
to tell us more about what is going on here. Could you try to enable
oom/reclaim_retry_zone and vmscan/mm_vmscan_direct_reclaim_{begin,end}
-- 
Michal Hocko
SUSE Labs