readprofile - read kernel profiling information
This manpage documents version 2.0 of the program.
The readprofile command uses the /proc/profile information to print ascii data on standard output. The output is organized in three columns: the first is the number of clock ticks, the second is the name of the C function in the kernel where those many ticks occurred, and the third is the normalized `load' of the procedure, calculated as a ratio between the number of ticks and the length of the procedure. The output is filled with blanks to ease readability.
-m, --mapfile mapfile
-M, --multiplier multiplier
-p, --profile pro-file
readprofile only works with a 1.3.x or newer kernel, because /proc/profile changed in the step from 1.2 to 1.3.
This program only works with ELF kernels. The change for a.out kernels is trivial, and left as an exercise to the a.out user.
To enable profiling, the kernel must be rebooted, because no profiling module is available, and it wouldn’t be easy to build. To enable profiling, you can specify profile=2 (or another number) on the kernel commandline. The number you specify is the two-exponent used as profiling step.
Profiling is disabled when interrupts are inhibited. This means that many profiling ticks happen when interrupts are re-enabled. Watch out for misleading information.
Browse the profiling buffer ordering by clock ticks:
readprofile | sort -nr | less
Print the 20 most loaded procedures:
readprofile | sort -nr +2 | head -20
Print only filesystem profile:
readprofile | grep _ext2
Look at all the kernel information, with ram addresses:
readprofile -av | less
Browse a 'frozen' profile buffer for a non current kernel:
readprofile -p ~/profile.freeze -m /zImage.map.gz
Request profiling at 2kHz per CPU, and reset the profiling buffer:
sudo readprofile -M 20
For bug reports, use the issue tracker at <https://github.com/util-linux/util-linux/issues>.
The readprofile command is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.