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On 04/20/2011 05:01 PM, Benjamin Herrenschmidt wrote:<br>
<span style="white-space: pre;">> On Wed, 2011-04-20 at 12:07
+0200, Peter Zijlstra wrote:<br>
>> On Thu, 2011-03-10 at 15:10 +0100, Peter Zijlstra wrote:<br>
>>> <br>
>>> Also, still waiting to hear from the Power7 folks on
how often<br>
>>> they think to rebuild the topology and how they think
that makes<br>
>>> sense, afaict Power7 does have actual NUMA nodes
unlike s390, so<br>
>>> I'm still not seeing how that's going to work
properly at all.<br>
>> <br>
>> Jesse care to answer? I hear from Ben you're responsible
for that<br>
>> mess.<br>
> <br>
> "responsible for this mess" is a big word :-)<br>
> <br>
> But he's the one to last play with that code ... Jesse ?<br>
> <br>
</span><br>
Hi Peter!<br>
<br>
According the the Power firmware folks, updating the home node of a
virtual cpu happens rather infrequently. The VPHN code currently
checks for topology updates every 60 seconds, but we can poll less
frequently if it helps. I chose 60 second intervals simply because
that's how often they check the topology on s390. ;-)<br>
<br>
As for updating the memory topology, there are cases where changing
the home node of a virtual cpu doesn't affect the memory topology.
If it does, there is a separate notification system for memory
topology updates that is independent from the cpu updates. I plan to
start working on a patch set to enable memory topology updates in
the kernel in the coming weeks, but I wanted to get the cpu patches
out on the list so we could start having these debates. :)<br>
<br>
Sincerely,<br>
<br>
Jesse Larrew<br>
Software Engineer, Linux on Power Kernel Team<br>
IBM Linux Technology Center<br>
Phone: (512) 973-2052 (T/L: 363-2052)<br>
<a class="moz-txt-link-abbreviated" href="mailto:jlarrew@linux.vnet.ibm.com">jlarrew@linux.vnet.ibm.com</a><br>
<br>
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