At 10/10/2012 05:51 PM, Peter Zijlstra Wrote: > On Wed, 2012-10-10 at 17:33 +0800, Wen Congyang wrote: >> >> Hmm, if per-cpu memory is preserved, and we can't offline and remove >> this memory. So we can't offline the node. >> >> But, if the node is hot added, and per-cpu memory doesn't use the >> memory on this node. We can hotremove cpu/memory on this node, and then >> offline this node. >> >> Before the cpu is hotadded, cpu's node is -1. We set cpu<->node mapping >> when it is hotadded. So the entire cpu<->node mapping was not invariant >> during hotplug. >> >> So it is why I try to clear it when the cpu is hot-removed. >> >> As we need the mapping to migrate a task to the cpu on the same node first, >> I think we can clear the mapping when the node is offlined. > > Hmm maybe, but hardware that can hot-add is rare and nobody has it so > nobody cares ;-) Yes, nobody cares it now. But we have a such hardware, so I care it now. > > But by clearing cpu_to_node on every hotplug you change semantics for > all hardware and everybody gets to feel the pain. > > I'm not saying you cannot change things, I'm only saying you should be > far more careful about it, not change it and wait for things to break. > Put in some effort to find things that might break and warn people -- > sure, you'll always miss some, and that's ok. I use ./scripts/get_maintainer.pl, and it doesn't tell me that I should cc you when I post that patch. -- To unsubscribe from this list: send the line "unsubscribe linux-numa" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
