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SubjectRe: [PATCH] mm: be more verbose for alloc_contig_range faliures
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On 18.02.21 10:35, Michal Hocko wrote:
> On Thu 18-02-21 10:02:43, David Hildenbrand wrote:
>> On 18.02.21 09:56, Michal Hocko wrote:
>>> On Wed 17-02-21 08:36:03, Minchan Kim wrote:
>>>> alloc_contig_range is usually used on cma area or movable zone.
>>>> It's critical if the page migration fails on those areas so
>>>> dump more debugging message like memory_hotplug unless user
>>>> specifiy __GFP_NOWARN.
>>>
>>> I agree with David that this has a potential to generate a lot of output
>>> and it is not really clear whether it is worth it. Page isolation code
>>> already has REPORT_FAILURE mode which currently used only for the memory
>>> hotplug because this was just too noisy from the CMA path - d381c54760dc
>>> ("mm: only report isolation failures when offlining memory").
>>>
>>> Maybe migration failures are less likely to fail but still.
>>
>> Side note: I really dislike that uncontrolled error reporting on memory
>> offlining path we have enabled as default. Yeah, it might be useful for
>> ZONE_MOVABLE in some cases, but otherwise it's just noise.
>>
>> Just do a "sudo stress-ng --memhotplug 1" and see the log getting flooded
>
> Anyway we can discuss this in a separate thread but I think this is not
> a representative workload.

Sure, but the essence is "this is noise", and we'll have more noise on
alloc_contig_range() as we see these calls more frequently. There should
be an explicit way to enable such *debug* messages.

--
Thanks,

David / dhildenb

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