Re: [PATCH] oom: print nodemask in the oom report

[Vlastimil Babka]

On 10/04/2016 04:16 PM, Michal Hocko wrote:
> On Tue 04-10-16 15:24:53, Vlastimil Babka wrote:
> > On 09/30/2016 11:41 PM, Michal Hocko wrote:
> [...]
> > > Fix this by always priting the nodemask. It is either mempolicy mask
> > > (and non-null) or the one defined by the cpusets.
> >
> > I wonder if it's helpful to print the cpuset one when that's printed
> > separately, and seeing both pieces of information (nodemask and cpuset)
> > unmodified might tell us more. Is it to make it easier to deal with NULL
> > nodemask? Or to make sure the info gets through pr_warn() and not pr_info()?
>
> I am not sure I understand the question. I wanted to print the nodemask
> separatelly in the same line with all other allocation request
> parameters like order and gfp mask because that is what the page
> allocator got (via policy_nodemask). cpusets builds on top - aka applies
> __cpuset_zone_allowed on top of the nodemask. So imho it makes sense to
> look at the cpuset as an allocation domain while the mempolicy as a
> restriction within this domain.
>
> Does that answer your question?

Ah, I wasn't clear. What I questioned is the fallback to cpusets for 
NULL nodemask:

nodemask_t *nm = (oc->nodemask) ? oc->nodemask : 
&cpuset_current_mems_allowed;

> > > The new output for
> > > the above oom report would be
> > >
> > > PoolThread invoked oom-killer: gfp_mask=0x280da(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), nodemask=0, order=0, oom_adj=0, oom_score_adj=0
> > >
> > > This patch doesn't touch show_mem and the node filtering based on the
> > > cpuset node mask because mempolicy is always a subset of cpusets and
> > > seeing the full cpuset oom context might be helpful for tunning more
> > > specific mempolicies inside cpusets (e.g. when they turn out to be too
> > > restrictive). To prevent from ugly ifdefs the mask is printed even
> > > for !NUMA configurations but this should be OK (a single node will be
> > > printed).
> > >
> > > Reported-by: Sellami Abdelkader <abdelkader.sellami@xxxxxxx>
> > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> >
> > Other than that,
> >
> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
>
> Thanks!