On Tuesday, July 25, 2017 8:42 PM, hal Hocko wrote: > On Tue 25-07-17 19:56:24, Wei Wang wrote: > > On 07/25/2017 07:25 PM, Michal Hocko wrote: > > >On Tue 25-07-17 17:32:00, Wei Wang wrote: > > >>On 07/24/2017 05:00 PM, Michal Hocko wrote: > > >>>On Wed 19-07-17 20:01:18, Wei Wang wrote: > > >>>>On 07/19/2017 04:13 PM, Michal Hocko wrote: > > >>>[... > > We don't need to do the pfn walk in the guest kernel. When the API > > reports, for example, a 2MB free page block, the API caller offers to > > the hypervisor the base address of the page block, and size=2MB, to > > the hypervisor. > > So you want to skip pfn walks by regularly calling into the page allocator to > update your bitmap. If that is the case then would an API that would allow you > to update your bitmap via a callback be s sufficient? Something like > void walk_free_mem(int node, int min_order, > void (*visit)(unsigned long pfn, unsigned long nr_pages)) > > The function will call the given callback for each free memory block on the given > node starting from the given min_order. The callback will be strictly an atomic > and very light context. You can update your bitmap from there. I would need to introduce more about the background here: The hypervisor and the guest live in their own address space. The hypervisor's bitmap isn't seen by the guest. I think we also wouldn't be able to give a callback function from the hypervisor to the guest in this case. > > This would address my main concern that the allocator internals would get > outside of the allocator proper. What issue would it have to expose the internal, for_each_zone()? I think new code which would call it will also be strictly checked when they are pushed to upstream. Best, Wei
