This is the kernel version of kstats.
You can apply the patch to a full kernel to build it statically,
or just build it as a module, using make in this directory.
Make sure you have the linux headers for your kernel
apt-get install build-essential linux-headers-$(uname -r)
dpkg -l linux-headers-$(uname -r)
For direct instrumentation of kernel code, follow the instructions
in include/linux/kstats.h .
An entry defined with kstats_new("foo", n) will appear
in /sys/kernel/debug/kstats/foo. Reading the file produces the current
state of the histogram, per-cpu.
To stop/start/reset collection do
echo {start|stop|reset} > /sys/kernel/debug/kstats/foo
For instrumentation of functions using debugfs, you can attach to kernel functions with the syntax
echo trace [pcpu:]function_name [bits n] > /sys/kernel/debug/kstats/_config
echo remove function_name > /sys/kernel/debug/kstats/_config
See details in kstats.c:ks_node_new() for supported commands.