Re: IB/cma: Make timeout dependent on the subnet timeout

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 04/25/14 04:59, Hefty, Sean wrote:
>> Sean, can't we have CMA to follow the same practice used in the CM where
>> we derive the RC QP timeout based on the packet life time retrieved in
>> path queries? e.g base the cm response time out on this value  too?
> 
> We could.  The timeout that's being modified by the patch is the time needed
> by the remote peer to process the incoming message and send a
response. This
> time is in addition to the packet life time value that gets used.
> 
> For a remote kernel agent, the time needed to respond to a CM message may be
> fairly small.  For a user space client, the time may be significant,
on the
> order to seconds to minutes.  We can probably make due with a fairly short
> timeout, provided that MRAs are used by the remote side.
> 
> There's no great solution that I can think of.  Maybe the RDMA CM can adjust
> the timeout based on the remote address, assuming that it can determine if
> the remote address is a user space or kernel agent.

Another possible approach is to make the CM timeout configurable for
kernel clients only. How about creating two versions of struct
rdma_conn_param - the existing version for communication between user
space and kernel and a second version for in-kernel clients only ? In
that second version a field could be added that allows to specify the CM
timeout.

Bart.

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