LddProfiling < Training2

%SECTION0{name=LddProfiling}% Profiling techniques

   * Profiling is a technique for discouvering performance bottlenecks

   * For Linux two techniques available:
      1) full coverage analysis with gcov [[http://lwn.net/Articles/284886/][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])*

<verbatim>
# 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

</verbatim>  


   * Further reading
      * [1] [[http://www.ibm.com/developerworks/systems/library/es-oprofile/][Profiling on Power]]
      * [2] [[http://oprofile.sourceforge.net/news/][OProfile Project]]
5.4.3. Debugging with Hardware Debuggers		1. Denx Training Topics		5.5. The Linux driver model
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