> How would you allow that guest to stay on 2 virtual CPUs but still > be able to hot-plug many other CPUs if the guest context rises above > its original CPU utilization? (unless you're planning to rewrite lots of possible cpu users all over the tree) -- the only way is to keep the percpu area small and preallocate. As long as the per cpu data size stays reasonable (not more than a 100-200k) that's very doable. It probably won't work with 4096 guest CPUs without wasting too much memory, but then I don't think we have any Hypervisor that scales to that many CPUs anyways, so it's not the biggest concern. For the 128CPU case it works (although i might need to enlarge vmalloc area a bit on 32bit) Unfortunately a few debugging subsystems seem to currently eat much more, but those just need to be fixed to only allocate state for actually running CPUs, not just possible ones. I suspect we need a scripts/percpubloat.pl -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
