[ofa-general] [RFC] [PATCH 0/5 v2] rdma/cm: add ability to specify type of service

[Sean Hefty]

>On the end stack side, has it been decided to ignore whether the SA
>indicates whether or not it supports QoS ? Wouldn't it be useful to
>have some warning message indicating this in the end node (that it
>might not be getting the service quality desired) ?

This is just my opinion, but...

This ends up adding a fair amount of complexity in order to display a simple
warning message.  The code is written to try for QoS, but use whatever is
available if QoS support is not enabled.  If we wanted to display a warning,
then I think that the user should have control over whether QoS support is
enabled on the host side, along with policy controls over what action to take in
case of a failure.  This support would need to be per ULP, and defined for each
node on the fabric.  Displaying a warning without the user explicitly asking for
QoS support can give the impression that something is wrong when things are
operating correctly.

The other complexity is that additional queuing becomes necessary for QoS
enabled PR queries.  It's possible for ULPs to request paths before the local SA
query code can determine whether or not the SA supports QoS.  I don't feel that
a warning message is necessarily worth the extra complexity, especially when
things like SA failover and IB routers get tossed into the mix.

- Sean