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Re: [PATCH] mm/memory hotplug: print the last vmemmap region at the end of hot add memory

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  Re: [PATCH] mm/memory hotplug: print the last vmemmap region at the  end of hot add memory Zhu Guihua <zhugh.fnst@cn.fujitsu.com> - 2015-06-09 05:50 +0200
    Re: [PATCH] mm/memory hotplug: print the last vmemmap region at the  end of hot add memory Zhu Guihua <zhugh.fnst@cn.fujitsu.com> - 2015-06-11 12:50 +0200

#1160952 — Re: [PATCH] mm/memory hotplug: print the last vmemmap region at the end of hot add memory

On 06/09/2015 07:30 AM, Andrew Morton wrote:
> On Mon, 8 Jun 2015 14:44:41 +0800 Zhu Guihua <zhugh.fnst@cn.fujitsu.com> wrote:
>
>> When hot add two nodes continuously, we found the vmemmap region info is a
>> bit messed. The last region of node 2 is printed when node 3 hot added,
>> like the following:
>> Initmem setup node 2 [mem 0x0000000000000000-0xffffffffffffffff]
>>   On node 2 totalpages: 0
>>   Built 2 zonelists in Node order, mobility grouping on.  Total pages: 16090539
>>   Policy zone: Normal
>>   init_memory_mapping: [mem 0x40000000000-0x407ffffffff]
>>    [mem 0x40000000000-0x407ffffffff] page 1G
>>    [ffffea1000000000-ffffea10001fffff] PMD -> [ffff8a077d800000-ffff8a077d9fffff] on node 2
>>    [ffffea1000200000-ffffea10003fffff] PMD -> [ffff8a077de00000-ffff8a077dffffff] on node 2
>> ...
>>    [ffffea101f600000-ffffea101f9fffff] PMD -> [ffff8a074ac00000-ffff8a074affffff] on node 2
>>    [ffffea101fa00000-ffffea101fdfffff] PMD -> [ffff8a074a800000-ffff8a074abfffff] on node 2
>> Initmem setup node 3 [mem 0x0000000000000000-0xffffffffffffffff]
>>   On node 3 totalpages: 0
>>   Built 3 zonelists in Node order, mobility grouping on.  Total pages: 16090539
>>   Policy zone: Normal
>>   init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
>>    [mem 0x60000000000-0x607ffffffff] page 1G
>>    [ffffea101fe00000-ffffea101fffffff] PMD -> [ffff8a074a400000-ffff8a074a5fffff] on node 2 <=== node 2 ???
>>    [ffffea1800000000-ffffea18001fffff] PMD -> [ffff8a074a600000-ffff8a074a7fffff] on node 3
>>    [ffffea1800200000-ffffea18005fffff] PMD -> [ffff8a074a000000-ffff8a074a3fffff] on node 3
>>    [ffffea1800600000-ffffea18009fffff] PMD -> [ffff8a0749c00000-ffff8a0749ffffff] on node 3
>> ...
>>
>> The cause is the last region was missed at the and of hot add memory, and
>> p_start, p_end, node_start were not reset, so when hot add memory to a new
>> node, it will consider they are not contiguous blocks and print the
>> previous one. So we print the last vmemmap region at the end of hot add
>> memory to avoid the confusion.
>>
>> ...
>>
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -513,6 +513,7 @@ int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
>>   			break;
>>   		err = 0;
>>   	}
>> +	vmemmap_populate_print_last();
>>   
>>   	return err;
>>   }
> vmemmap_populate_print_last() is only available on x86_64, when
> CONFIG_SPARSEMEM_VMEMMAP=y.  Are you sure this won't break builds?

I tried this on i386 and on x86_64 when CONFIG_SPARSEMEM_VMEMMAP=n ,
it builds ok.

Thanks,
Zhu

>
> .
>

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#1163133

On 06/10/2015 04:29 AM, Andrew Morton wrote:
> On Tue, 9 Jun 2015 11:41:28 +0800 Zhu Guihua <zhugh.fnst@cn.fujitsu.com> wrote:
>
>>>> --- a/mm/memory_hotplug.c
>>>> +++ b/mm/memory_hotplug.c
>>>> @@ -513,6 +513,7 @@ int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
>>>>    			break;
>>>>    		err = 0;
>>>>    	}
>>>> +	vmemmap_populate_print_last();
>>>>    
>>>>    	return err;
>>>>    }
>>> vmemmap_populate_print_last() is only available on x86_64, when
>>> CONFIG_SPARSEMEM_VMEMMAP=y.  Are you sure this won't break builds?
>> I tried this on i386 and on x86_64 when CONFIG_SPARSEMEM_VMEMMAP=n ,
>> it builds ok.
> With powerpc:
>
> akpm3:/usr/src/25> make allmodconfig
> akpm3:/usr/src/25> make mm/memory_hotplug.o
> akpm3:/usr/src/25> nm mm/memory_hotplug.o | grep vmemmap_populate_print_last
> 	U .vmemmap_populate_print_last
> akpm3:/usr/src/25> grep -r vmemmap_populate_print_last arch/powerpc
> akpm3:/usr/src/25>
>
> So I think that's going to break.
>
> I expect ia64 will break also, but I didn't investigate.
> .
>

There is
void __weak __meminit vmemmap_populate_print last(void)
in /mm/sparse.c, so I think this won't break builds.

And I found the function was invoked in void __init sparse_init(void) 
without
CONFIG_SPARSEMEM_VMEMMAP=y.

I also tried this on arm, it builds ok too.

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