On Mon 05-11-12 14:33:12, David Rientjes wrote: > On Mon, 5 Nov 2012, KY Srinivasan wrote: > > > The Hyper-V host has a policy engine for managing available physical memory across > > competing virtual machines. This policy decision is based on a number of parameters > > including the memory pressure reported by the guest. Currently, the pressure calculation is > > based on the memory commitment made by the guest. From what I can tell, the ratio of > > currently allocated physical memory to the current memory commitment made by the guest > > (vm_committed_as) is used as one of the parameters in making the memory balancing decision on > > the host. This is what Windows guests report to the host. So, I need some measure of memory > > commitments made by the Linux guest. This is the reason I want export vm_committed_as. > > > > I don't think you should export the symbol itself to modules but rather a > helper function that returns s64 that just wraps > percpu_counter_read_positive() which your driver could use instead. Agreed, we should rather make sure that nobody can manipulate the value from modules. > (And why percpu_counter_read_positive() returns a signed type is a > mystery.) Strange indeed. The last commit changed it from long to s64 to suport values bigger than 2^31 but even the original long doesn't make much sense to me. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>