ps doesn't respect -o cpu keyword

[pluknet]

Hi.

I noticed that ps on all supported releases (w/ ULE)
shows the value of cpu keyword always as 0 (zero).

COMMAND               CPU
kernel/swapper          0
kernel/firmware taskq   0
kernel/thread taskq     0
kernel/kqueue taskq     0
kernel/acpi_task_0      0
kernel/acpi_task_1      0
kernel/acpi_task_2      0
kernel/igb0 taskq       0
kernel/igb1 taskq       0
init                    0
g_event                 0
g_up                    0
g_down                  0
xpt_thrd                0
sctp_iterator           0
pagedaemon              0
vmdaemon                0
pagezero                0
audit                   0
idle/idle: cpu2         0
idle/idle: cpu1         0

P.S.
That's only for ps; top is not affected.
  PID USERNAME      PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
   11 root          171 ki31     0K    24K RUN     0 117.2H 43.46% {idle: cpu0}
   11 root          171 ki31     0K    24K RUN     2 115.3H 40.28% {idle: cpu2}
   11 root          171 ki31     0K    24K CPU1    1 103.1H 36.67% {idle: cpu1}
   12 root          -68    -     0K   184K CPU0    0 981:19 22.75%
{irq260: igb1}
    0 root          -68    0     0K    64K -       1 200:18  1.07% {igb1 taskq}
   12 root          -32    -     0K   184K WAIT    1  55:24  0.59% {swi4: clock}
   12 root          -68    -     0K   184K WAIT    2 310:31  0.29%
{irq259: igb1}
   12 root          -40    -     0K   184K WAIT    0   5:48  0.20%
{swi2: cambio}
    4 root           -8    -     0K     8K -       2  26:21  0.00% g_down
64298 root           44    0 10748K  6776K select  2  23:06  0.00% snmpd
   16 root           44    -     0K     8K syncer  2  22:22  0.00% syncer
   12 root          -64    -     0K   184K WAIT    1  16:22  0.00% {irq32: sym0}
   13 root           44    -     0K     8K -       0  13:55  0.00% yarrow
   12 root          -44    -     0K   184K WAIT    2  11:39  0.00%
{swi1: netisr 0}

-- 
wbr,
pluknet