5.4.4. Profiling techniques

• Profiling is a technique for discouvering performance bottlenecks

• For Linux two techniques available:
  1. ) full coverage analysis with gcov LWN article
     • not included in mainline
     • kernel only
  2. ) statistical profiling with OProfile[2]
     • included in mainline and ELDK contains userspace support
     • works out of the box for kernel and userspace

• OProfile
  • Enable in Kernel:
    • General Setup -> Profiling Support (Experimental)
    • Kernel Hacking -> Compile Kernel with Debug Info

simple session (multiply example taken from [1])

# initalize oprof
$ opcontrol --init

# where's our kernel?
$ opcontrol --vmlinux=/tmp/vmlinux

# clear old data
$ opcontrol --reset

# available events?
$ opcontrol -l

# start daemon and start collecting data
$ opcontrol --start

# run application
$ while ./multiply; do ./multiply; echo -n .; done
......... 

# dump data to daemon
$ opcontrol --dump

# stop daemon
$ opcontrol --stop

# examine
$ opcontrol -l ./multiply

# annotate
$ opannotate -s ./multiply

• Further reading
  • [1] Profiling on Power
  • [2] OProfile Project