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SubjectRe: [PATCH] x86: only clear node_states for 64bit
Andrew Morton wrote:
> On Mon, 22 Jun 2009 08:38:50 -0700
> Yinghai Lu <yinghai@kernel.org> wrote:
>
>> Nathan reported that
>> | commit 73d60b7f747176dbdff826c4127d22e1fd3f9f74
>> | Author: Yinghai Lu <yinghai@kernel.org>
>> | Date: Tue Jun 16 15:33:00 2009 -0700
>> |
>> | page-allocator: clear N_HIGH_MEMORY map before we set it again
>> |
>> | SRAT tables may contains nodes of very small size. The arch code may
>> | decide to not activate such a node. However, currently the early boot
>> | code sets N_HIGH_MEMORY for such nodes. These nodes therefore seem to be
>> | active although these nodes have no present pages.
>> |
>> | For 64bit N_HIGH_MEMORY == N_NORMAL_MEMORY, so that works for 64 bit too
>>
>> the cpuset.mems cgroup attribute on an i386 kvm guest
>>
>> fix it by only clearing node_states[N_NORMAL_MEMORY] for 64bit only.
>> and need to do save/restore for that in find_zone_movable_pfn
>>
>
> There appear to be some words omitted from this changelog - it doesn't
> make sense.
>
> I think that perhaps a line got deleted before "the cpuset.mems cgroup
> ...". That was the line which actualy describes the bug which we're
> fixing. Or perhaps it was a single word? "zeroes".
>
>
> I did this:
>
> Nathan reported that
> :
> : | commit 73d60b7f747176dbdff826c4127d22e1fd3f9f74
> : | Author: Yinghai Lu <yinghai@kernel.org>
> : | Date: Tue Jun 16 15:33:00 2009 -0700
> : |
> : | page-allocator: clear N_HIGH_MEMORY map before we set it again
> : |
> : | SRAT tables may contains nodes of very small size. The arch code may
> : | decide to not activate such a node. However, currently the early boot
> : | code sets N_HIGH_MEMORY for such nodes. These nodes therefore seem to be
> : | active although these nodes have no present pages.
> : |
> : | For 64bit N_HIGH_MEMORY == N_NORMAL_MEMORY, so that works for 64 bit too
> :

"
> : unintentionally and incorrectly clears the cpuset.mems cgroup attribute on
> : an i386 kvm guest
"
==>
32bit assume NORMAL_MEMORY bit and HIGH_MEMORY bit are set for Node0 always.

and some code only check if HIGH_MEMORY is there to know if NORMAL_MEMORY is there.

YH



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