FSS not working properly?

gistfile1.txt

# zonecfg -z $build "info brand ; info cpu-shares ; info capped-cpu" ; zonecfg -z $build2 "info brand ; info cpu-shares ; info capped-cpu"
brand: joyent
[cpu-shares: 20000]
brand: joyent
[cpu-shares: 10000]


[root@lava ~]# prctl -n zone.cpu-shares $(ps -z $build -o pid | tail -1)
process: 13350: /bin/bash ./busy 200
NAME    PRIVILEGE       VALUE    FLAG   ACTION                       RECIPIENT
zone.cpu-shares
        usage           20.0K    
        privileged      20.0K       -   none                                 -
        system          65.5K     max   none                                 -
[root@lava ~]# prctl -n zone.cpu-shares $(ps -z $build2 -o pid | tail -1)
process: 13971: /bin/bash ./busy 200
NAME    PRIVILEGE       VALUE    FLAG   ACTION                       RECIPIENT
zone.cpu-shares
        usage           10.0K    
        privileged      10.0K       -   none                                 -
        system          65.5K     max   none    
        -
[root@lava ~]# mpstat -a 1 3 | tail -2
SET minf mjf xcal  intr ithr  csw icsw migr smtx  srw syscl  usr sys  wt idl sze
  0   23   0    0  8199  303 5967 5570 1570   84    0   661  100   0   0   0  56


[root@lava ~]# prstat -cZ
Please wait...
   PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP       
 13366 root     3388K 1500K run      1    0   0:01:03 0.3% busy/1
 13466 root     3408K 1520K run      1    0   0:01:09 0.3% busy/1
...
ZONEID    NPROC  SWAP   RSS MEMORY      TIME  CPU ZONE                        
    16      219   85M   49M   0.0%   3:40:27  50% 4c0756b2-590b-4e5e-b8a8-b3ea6f9111b3
    17      219   85M   50M   0.0%   2:21:23  50% 91aa12ac-77ba-e330-9ce3-85385a71bf55
     0       58  253M  245M   0.1%   0:02:21 0.0% global                      
Total: 496 processes, 1330 lwps, load averages: 400.64, 417.36, 345.11



  pid    tid zid prd tks opr npr prn ps% zrtck      shusage         prjuse
14654  30977  16   1   0   1   1  56  66 27854    250811712      111471872
14649  30972  16   1   0   1   1  56  66 27854    250811712      111471872
14642  30965  16   1   0   1   1  56  66 27854    250811712      111471872
14624  30947  16   1   0   1   1  56  66 27854    250811712      111471872
14576  30898  17   1   0   1   1  56  33 27910   1003759164      111528796
14568  30890  17   1   0   1   1  56  33 27910   1003759164      111528796
14555  30877  17   1   0   1   1  56  33 27910   1003759164      111528796
14652  30975  16   1   0   1   1  56  66 27854    250811712      111471872


I occasionally see priority bumps here, but seemingly applied across the shares:

  pid    tid zid prd tks opr npr prn ps% zrtck      shusage         prjuse
14653  30976  16   1   0   1  17  56  66 27854    250811712      111471872
14641  30964  16   1   0   1  17  56  66 27854    250811712      111471872
14583  30905  17   1   0   1  17  56  33 27910   1003759164      111528796
14575  30897  17   1   0   1  17  56  33 27910   1003759164      111528796