Re: 4.8.8 kernel trigger OOM killer repeatedly when I have lots of RAM that should be free

[Simon Kirby <sim@hostway.ca>]

On Tue, Nov 22, 2016 at 05:14:02PM +0100, Vlastimil Babka wrote:

> On 11/22/2016 05:06 PM, Marc MERLIN wrote:
> > On Mon, Nov 21, 2016 at 01:56:39PM -0800, Marc MERLIN wrote:
> >> On Mon, Nov 21, 2016 at 10:50:20PM +0100, Vlastimil Babka wrote:
> >>>> 4.9rc5 however seems to be doing better, and is still running after 18
> >>>> hours. However, I got a few page allocation failures as per below, but the
> >>>> system seems to recover.
> >>>> Vlastimil, do you want me to continue the copy on 4.9 (may take 3-5 days) 
> >>>> or is that good enough, and i should go back to 4.8.8 with that patch applied?
> >>>> https://marc.info/?l=linux-mm&m=147423605024993
> >>>
> >>> Hi, I think it's enough for 4.9 for now and I would appreciate trying
> >>> 4.8 with that patch, yeah.
> >>
> >> So the good news is that it's been running for almost 5H and so far so good.
> > 
> > And the better news is that the copy is still going strong, 4.4TB and
> > going. So 4.8.8 is fixed with that one single patch as far as I'm
> > concerned.
> > 
> > So thanks for that, looks good to me to merge.
> 
> Thanks a lot for the testing. So what do we do now about 4.8? (4.7 is
> already EOL AFAICS).
> 
> - send the patch [1] as 4.8-only stable. Greg won't like that, I expect.
>   - alternatively a simpler (againm 4.8-only) patch that just outright
> prevents OOM for 0 < order < costly, as Michal already suggested.
> - backport 10+ compaction patches to 4.8 stable
> - something else?
> 
> Michal? Linus?
> 
> [1] https://marc.info/?l=linux-mm&m=147423605024993

Sorry for my molasses rate of feedback. I found a workaround, setting
vm/watermark_scale_factor to 500, and threw that in sysctl. This was on
the MythTV box that OOMs everything after about a day on 4.8 otherwise.

I've been running [1] for 9 days on it (4.8.4 + [1]) without issue, but
just realized I forgot to remove the watermark_scale_factor workaround.
I've restored that now, so I'll see if it becomes unhappy by tomorrow.

I also threw up a few other things you had asked for (vmstat, zoneinfo
before and after the first OOM on 4.8.4): http://0x.ca/sim/ref/4.8.4/
(that was before booting into a rebuild with [1] applied)

Simon-

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