Problem with chrt

[JD]

  I am trying to run a command in realtime mode just to see
if it behaves any different as far as timings are concerned.

Man page says:


CHRT(1) Linux User’s Manual CHRT(1)

NAME
chrt - manipulate real-time attributes of a process

SYNOPSIS
chrt [options] prio command [arg]...
chrt [options] -p [prio] pid

So, I tried the first example instance above:

$ sudo chrt 0 ./freq -s120 -u0 -r
chrt: failed to set pid 0's policy: Invalid argument

Hmmm. I thought the arg after chrt should be the value of the priority, 
since options to chrt are optional!!!

Another broken utility???

Soo I tried:

$ sudo chrt ./freq -s120 -u0 -r # i.e. no value for priority
chrt: failed to set pid 0's policy: Invalid argument

Anyone tried this before? Any clues?