On 9/6/2015 9:45 AM, Christoph Hellwig wrote:
Hi All,
right now RDMA/CM works on a QP basis, but seems very awakward if you
want multiple QPs as part of a single logical device, which will be
useful for a lot of modern protocols. For example we will need to check
in the CM handler that we're not getting a different ib_device if we
want to apply the device limit in any sort of global scope, and it's
generally very hard to get a struct ib_device that can be used as
a driver model parent.
Is there any interest in trying to add an API to the CM to do a single
address resolution and allocate multiple QPs with these checks in
place?
Hi Christoph,
The CM is responsible of establishing an RDMA channel. What you are
referring to is a concept of a session. I'm not entirely sure how we can
fit a model where the CM establishes a multi-channel session as the
CM request contains a (single) source QPN. So there is a 1-1
relationship between a cm_id and a queue-pair. The device handle depends
on the address resolution to the end-node.
I assume we can think of some form of an rdma_session which will manage
multiple cm_id's (that belongs to a single address resolution), call
the ULP to allocate their corresponding queue-pairs and send a connect
request for each one. Such an rdma_session can verify the same ib_device
handle on all the cm_id's. But I'm not sure how such a concept would
impact on aspects such as event handling etc...
Sagi.
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