Re: [PATCH v2 10/10] nvmet: Optionally use PCI P2P memory

Logan Gunthorpe
2018-03-01T19:10:12Z

> Wouldn't it all be simpler if the p2p_dev resolution would be private
> to the namespace?
>
> So is adding some all the namespaces in a subsystem must comply to
> using p2p? Seems a little bit harsh if its not absolutely needed. Would
> be nice to export a subsystems between two ports (on two HCAs, across
> NUMA nodes) where the home node (primary path) would use p2p and
> failover would use host memory...
>
> Can you help me understand why this is absolutely not feasible?

Yes, it would simplify things. However, as best as I can tell, when we
allocate memory we don't know what namespace it will be used for. If
there is a way, I could probably rework it so there's a P2P device per
namespace.

Can you show me how we'd know the namespace to use in
nvmet_rdma_map_sgl_keyed()?

Thanks,

Logan