On 01/12/2018 08:33 PM, Michael Ellerman wrote:

Nathan Fontenot [off-list ref] writes:

...

quoted

One thing I don't see addressed in the comments or in the code is
migration support. I think we need to update the thread group mask
post-migration to reflect the threads per core on the new system.

Normally I'd agree with you, but I don't see any prospect of the kernel
surviving if the threads per core changes across a migration. We'll have
data structures allocated based on the old value and things will
definitely crash if the value increases. If it shrinks maybe we'd get
away with it, but either way is dicey.

If there's an expectation that we'll be able to migrate between systems
with different settings then we have a much bigger problem.

cheers

From what I recall of my tests a few months ago, the device-tree is read in

and flattened before the kernel starts processing the migration state.
I am trying to get access to a couple of P9 systems on which I may test
migration to verify the ordering of events between initializing the kernel
and post-migration processing.

Regards,

-- 
Michael W. Bringmann
Linux Technology Center
IBM Corporation
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External: (512) 286-5196
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