On 05/04/2017 02:46 PM, Michal Hocko wrote: > On Thu 04-05-17 14:33:24, Vlastimil Babka wrote: >>> >>> I am pretty sure s390 and ppc support NUMA and aim at supporting really >>> large systems. >> >> I don't see ppc there, > > config KVM_BOOK3S_64_HV > tristate "KVM for POWER7 and later using hypervisor mode in host" > depends on KVM_BOOK3S_64 && PPC_POWERNV > select KVM_BOOK3S_HV_POSSIBLE > select MMU_NOTIFIER > select CMA > > fa61a4e376d21 tries to explain some more
Uh, that's unfortunate then. > [...] >>> Are we really ready to add another thing like that? How are distribution >>> kernels going to handle that? >> >> I still hope that generic enterprise/desktop distributions can disable >> it, and it's only used for small devices with custom kernels. >> >> The config burden is already there in any case, it just translates to >> extra migratetype and fastpath hooks, not extra zone and potentially >> less nodes. > > AFAIU the extra migrate type costs nothing when there are no cma > reservations. And those hooks can be made noop behind static branch > as well. So distribution kernels do not really have to be afraid of > enabling CMA currently. The tradeoff is unfortunate :/
