Timing Measurements of Linux kernel routine

Question

Hi,

I added some additional code to the Linux kernel (the scheduler) and now I would like to know what is the impact of this modification.

For user processes I always used:

clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ...);

Now I am wondering if there is a kernel-equivalent routine that I could use to do something similar.

Many thanks for your assistance, Martin

Answer 1

Take a look at ftrace. Latencytop is based on that. There are good articles at lwn (here, here, and here)

Measuring scheduler performance is notoriously hard, so good luck :)

Answer 2

unsigned long long native_sched_clock(void); from asm/timer.h for x86

unsigned long long sched_clock(void); from linux/sched.h for any arch

They are wrappers around rdtsc - tick counter reader.

upd.

there is also linux/clocksource.h

timecounter_init - initialize a time counter
timecounter_read - return nanoseconds elapsed since timecounter_init()