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From:   Logan Gunthorpe <logang@deltatee.com>
Message-ID: <7163af93-2f37-a8b6-986a-3cb2e62bee29@deltatee.com>
Date:   Thu, 1 Mar 2018 12:10:12 -0700
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Subject: Re: [PATCH v2 10/10] nvmet: Optionally use PCI P2P memory
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> 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