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

[Zhu Guihua]

On 06/09/2015 07:30 AM, Andrew Morton wrote:
> On Mon, 8 Jun 2015 14:44:41 +0800 Zhu Guihua <zhugh.fnst@xxxxxxxxxxxxxx> 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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