Getting More Detailed Output On The Modules - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Chapter 39. OProfile
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The data is the same as the -l option except that for each symbol, each virtual memory address
used is shown. For each virtual memory address, the number of samples and percentage of
samples relative to the number of samples for the symbol is displayed.
-x<symbol-name>
Exclude the comma-separated list of symbols from the output.
session:<name>
Specify the full path to the session or a directory relative to the /var/lib/oprofile/samples/
directory.

39.5.3. Getting more detailed output on the modules

OProfile collects data on a system-wide basis for kernel- and user-space code running on the
machine. However, once a module is loaded into the kernel, the information about the origin of the
kernel module is lost. The module could have come from the initrd file on boot up, the directory with
the various kernel modules, or a locally created kernel module. As a result when OProfile records
sample for a module, it just lists the samples for the modules for an executable in the root directory,
but this is unlikely to be the place with the actual code for the module. You will need to take some
steps to make sure that analysis tools get the executable.
For example on an AMD64 machine the sampling is set up to record "Data cache accesses" and "Data
cache misses" and assuming you would like to see the data for the ext3 module:
$ opreport /ext3
CPU: AMD64 processors, speed 797.948 MHz (estimated)
Counted DATA_CACHE_ACCESSES events (Data cache accesses) with a unit mask of 0x00 (No unit
mask) count 500000
Counted DATA_CACHE_MISSES events (Data cache misses) with a unit mask of 0x00 (No unit mask)
count 500000
DATA_CACHE_ACC...|DATA_CACHE_MIS...|
samples| %| samples|
------------------------------------
148721 100.000 1493 100.000 ext3
To get a more detailed view of the actions of the module, you will need to either have the module
unstripped (e.g. installed from a custom build) or have the debuginfo RPM installed for the kernel.
Find out which kernel is running, "uname -a", get the appropriate debuginfo rpm, and install on the
machine.
Then make a symbolic link so oprofile finds the code for the module in the correct place:
# ln -s /lib/modules/`uname -r`/kernel/fs/ext3/ext3.ko /ext3
Then the detailed information can be obtained with:
# opreport image:/ext3 -l|more
544
8.3333
8.3333
8.3333
8.3333
8.3333
8.3333
%|