[openib-general] question on QoS support

[Hal Rosenstock]

Hi Oliver,

On Wed, 2006-11-01 at 16:52, Oliver wrote:
> Hi, folks -
> 
> I am trying to verify and evaluate IB QoS support, running openSM as
> subnet manager. The perftest program is extended to set SL as command
> line options instead of default 0, and by modifying VL arbitration
> tables, I am expecting to see the traffic shaping can actually take
> place,

How is this being observed/measured ?

>  but it did not.  More details on configuration:
> 
> in opensm.opts:
> # QoS default options
> qos_high_limit 255 # disable low priority table

This doesn't disable it but it won't be scheduled unless there are no
high priority packets to send.

> qos_vlarb_high: 0:4,1:4,2:8,3:0, 4:0 .... # this is to give VL 2
> (corresponding to SL 2) a higher weight 8
> qos_sl2vl 0,1,2,3,4, ... # no changes here
> 
> I think (though not verified) the Voltaire HCA we are using can
> support 8 data VLs.

Yes, 8 VLs should be supported in your subnet. You can verify this with
smpquery portinfo on the HCA port and examine OperVLs assuming the port
is ACTIVE.

>  I don't have much more information to go on why
> qos shaping is not taking place, any suggestions?

Sasha's email is a good start. We can go from there.

> A related question is, if I modify qos setting in SM, do I need to
> restart SA on each hosts for it to see the changes? (I am hoping not,
> as I tried in the test, it doesn't seem to make a difference)

Not sure what you mean. SA is tightly coupled with the OpenSM. Do you
mean SA client ? The client hosts don't need restarting but did you
restart OpenSM with your QoS configuration ?

BTW, which OpenSM are you running ?

-- Hal

> Thanks for help.