My approach would be to shape the sub-interface to a given level first, then
apply CBWFQ under that, identifying any specific traffic after the shaped
rate has been set. You can shape to 100% if you don't know the bandwidth
allocation as follows:

policy-map parent
class class-default
shape average percent 100
service-policy child

policy-map child
class class1
bandwidth percent 20

int serial 1.1
service-policy-out parent

If you apply this configu, you get the following output which shows the
overall rate for the sub-interface and 20% of the bandwidth guaranteed for
the traffic you want.


 Service-policy output: parent

   Class-map: class-default (match-any)
     0 packets, 0 bytes
     5 minute offered rate 0 bps, drop rate 0 bps
     Match: any
     Traffic Shaping
          Target/Average   Byte   Sustain   Excess    Interval  Increment
            Rate           Limit  bits/int  bits/int  (ms)      (bytes)
             100 (%)                0 (ms)      0 (ms)
         1544000/1544000   9650   38600     38600     25        4825

       Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping
       Active Depth                         Delayed   Delayed   Active
       -      0         0         0         0         0         no

     Service-policy : child

       Class-map: class1 (match-all)
         0 packets, 0 bytes
         5 minute offered rate 0 bps, drop rate 0 bps
         Match: access-group name FORS1.1
         Queueing
           Output Queue: Conversation 73
           Bandwidth 20 (%)
           Bandwidth 308 (kbps) Max Threshold 64 (packets)
           (pkts matched/bytes matched) 0/0
       (depth/total drops/no-buffer drops) 0/0/0

       Class-map: class-default (match-any)
         0 packets, 0 bytes
         5 minute offered rate 0 bps, drop rate 0 bps
         Match: any

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