Re: [discuss] Re: x86_64: 2.6.14-rc4 swiotlb broken

[Ravikiran G Thirumalai <kiran@scalex86.org>]

On Tue, Oct 18, 2005 at 11:29:18AM +0900, Yasunori Goto wrote:
> Hello. Linus-san.
> ... 
> In our making IA64 machine node 0 might not have any low-memory, and
> another node can have low-memory instead.
> 
> This cause comes from hotplug whole of one node.
> For example, please imagine following case.
> 
> 1) In this case, firmware remembers pxm 1's node has low memory.
> 
>                  node 0             node 1 
>                +--------------+  +-----------+
>                |  pxm = 1     |  | pxm = 2   |
>                |  low memory  |  |           |
>                +--------------+  +-----------+
> 
> 
> 2) If one node is hot-added at pxm = 0 (pxm is decided from physical
>    locate by firmware.), new node will be node 2.
> 
>   node 2          node 0          node 1 
> +-----------+  +--------------+  +-----------+
> | pxm = 0   |  |  pxm = 1     |  | pxm = 2   |
> |           |  |  low memory  |  |           |
> +-----------+  +--------------+  +-----------+
> 
> 3) If user reboots the machine, Linux decides node id from pxm's order.
>    But firmware still remembers which node has low memory.
>    So, node 0 will not have any low memory.
> 
>   node 0          node 1          node 2
> +-----------+  +--------------+  +-----------+
> | pxm = 0   |  |  pxm = 1     |  | pxm = 2   |
> |           |  |  low memory  |  |           |
> +-----------+  +--------------+  +-----------+
> 
> So, just "use NODE(0)" is not enough hack for our machine.
> If "use NODE(0)" is selected, kernel must sort pgdat link and
> node id by memory address. I think that hot add code will be a 
> bit messy instead.

Yasunori-san,
Does this patch work on your boxes instead? (For 2.6.14)
http://marc.theaimsgroup.com/?l=linux-kernel&m=112959469914681&w=2

Thanks,
Kiran
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