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READPROFILE !!!READPROFILE NAME SYNOPSIS VERSION DESCRIPTION EXAMPLES BUGS FILES ---- !!NAME readprofile - a tool to read kernel profiling information !!SYNOPSIS __readprofile__ [[ ''options'' ] !!VERSION This manpage documents version 2.0 of the program. !!DESCRIPTION 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. Available command line options are the following: -m __mapfile__ Specify a mapfile, which by default is __/usr/src/linux/System.map.__ You should specify the map file on cmdline if your current kernel isn't the last one you compiled. If the name of the map file ends with `.gz' it is decompressed on the fly. -p __pro-file__ Specify a different profiling buffer, which by default is __/proc/profile.__ Using a different pro-file is useful if you want to `freeze' the kernel profiling at some time and read it later. The __/proc/profile__ file can be copied using `cat' or `cp'. There is no more support for compressed profile buffers, like in __readprofile-1.1,__ because the program needs to know the size of the buffer in advance. __-i__ Info. This makes __readprofile__ only print the profiling step used by the kernel. The profiling step is the resolution of the profiling buffer, and is chosen during kernel configuration (through `make config'), or in the kernel's command line. If the __-t__ (terse) switch is used together with __-i__ only the decimal number is printed. __-a__ Print all symbols in the mapfile. By default the procedures with 0 reported ticks are not printed. __-r__ Reset the profiling buffer. This can only be invoked by root, because __/proc/profile__ is readable by everybody but writable only by the superuser. However, you can make __readprofile__ setuid 0, in order to reset the buffer without gaining privileges. -M __multiplier__ On some architectures it is possible to alter the frequency at which the kernel delivers profiling interrupts to each CPU. This option allows you to set the frequency, as a multiplier of the system clock frequency, HZ. This is supported on i386-SMP (2.2 and 2.4 kernel) and also on sparc-SMP and sparc64-SMP (2.4 kernel). This option also resets the profiling buffer, and requires superuser privileges. __-v__ Verbose. The output is organized in four columns and filled with blanks. The first column is the RAM address of a kernel function, the second is the name of the function, the third is the number of clock ticks and the last is the normalized load. __-V__ Version. This makes __readprofile__ print its version number and exit. !!EXAMPLES 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 `freezed' 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 !!BUGS __readprofile__ only works with an 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 Profiling is disabled when interrupts are inhibited. This means that many profiling ticks happen when interrupts are re-enabled. Watch out for misleading information. !!FILES /proc/profile A binary snapshot of the profiling buffer. /usr/src/linux/System.map The symbol table for the kernel. /usr/src/linux/* The program being profiled :-) ----
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