(8/12/13 1:23 PM), H. Peter Anvin wrote:
On 08/12/2013 10:01 AM, Tang Chen wrote:
I'm just thinking of a more extreme case. For example, if a machine
has only one node hotpluggable, and the kernel resides in that node.
Then the system has no hotpluggable node.
Yeah, sure, then there's no way that node can be hotpluggable and the
right thing to do is booting up the machine and informing the userland
that memory is not hotpluggable.
If we can prevent the kernel from using hotpluggable memory, in such
a machine, users can still do memory hotplug.
I wanted to do it as generic as possible. But yes, finding out the
nodes the kernel resides in and make it unhotpluggable can work.
Short of being able to remap memory under the kernel, I don't think
this can be very generic and as a compromise trying to keep as many
hotpluggable nodes as possible doesn't sound too bad.
I think making one of the node hotpluggable is better. But OK, it is
no big deal. There won't be such machine in reality, I think. :)
The user may very well have configured a system with mirrored memory for
the kernel node as that will be non-hotpluggable, but not for the
others. One can wonder how much that actually buys in real life, but
still...
Note. Such system is much cheaper than full memory mirroring system. That's
one of reason why server vendors are interesting in hot plugging.
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