Re: [PATCH v1 5/5] mm/memory_hotplug: print only with DEBUG_VM in online/offline_pages()

[David Hildenbrand]

On 17.08.2018 10:18, Oscar Salvador wrote:
>>  failed_addition:
>> +#ifdef CONFIG_DEBUG_VM
>>  	pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
>>  		 (unsigned long long) pfn << PAGE_SHIFT,
>>  		 (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
>> +#endif
> 
> I have never been sure about this.
> IMO, if I fail to online pages, I want to know I failed.
> I think that pr_err would be better than pr_debug and without CONFIG_DEBUG_VM.

I consider both error messages only partially useful, as

1. They only catch a subset of actual failures the function handles.
   E.g. onlining will not report an error message if the memory notifier
   failed.
2. Onlining/Offlining is usually (with exceptions - e.g. onlining during
   add_memory) triggered from user space, where we present an error
   code. At any times, the actual state of the memory blocks can be
   observed by querying the state.

I would even vote for dropping the two error case messages completely.
At least I don't consider them very useful.

> 
> But at least, if not, envolve it with a CONFIG_DEBUG_VM, but change pr_debug to pr_info.
> 
>> +#ifdef CONFIG_DEBUG_VM
>>  	pr_debug("memory offlining [mem %#010llx-%#010llx] failed\n",
>>  		 (unsigned long long) start_pfn << PAGE_SHIFT,
>>  		 ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
>> +#endif
> 
> Same goes here.
> 
> Thanks
> 


-- 

Thanks,

David / dhildenb