some questions about kernel debugging

[loody]

Dear all:
I enable kernel hacking options about kernel debugging on my mips platform.
I can successfully connect to the target board.
My question is:
1. why I cannot p/x the value of variable?
    I have enabled CONFIG_ARCH_WANT_FRAME_POINTERS and CONFIG_FRAME_POINTER
    but I still get the message which tell me "value optimized out".
    did I miss anything?
    my kernel version is 2.6.30.9?
appreciate your help,
miloody