Kernel Profiling: suggestions plz

Hi Buddies,
            Currenty am using Xilinx ML310 FPGA board and am running
PPC(32) linux on it.Now I want to profile kernel, like I want to run an
application and start kernel profiling and as application is finished I
want to stop kernel profiling and investigate where kernel is spending
more time.

            I tried gprof for user space programs ...it was fine..but I
dont know how to do kernel space profiling .Do I need to add any
patches ?.

  Can anyone suggest me what is /proc/porofile..because when I read ppc
embedded linux doc, it says kernel profiling can be done through
booting with option "profile=2" I have done and found /proc/profile.But
when I used "readprofile" it says /usr/src/linux/System.map doen't
exists.

usually when I cross compile and build new Image for my target... an
empty System.map file is created ...why it happens?


Could any of you can advice me some methods hot to profile kernel
running on PPC(32)

anticipating for your kind suggestions....thanks a lot..


regards
Jaggu