A simple DTrace userland example on FreeBSD

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System used:

FreeBSD hostmaster1.example.com 9.1-STABLE FreeBSD 9.1-STABLE #0 r248486: Thu Jun 13 00:23:59 CEST 2013     root@hostmaster1.example.com:/usr/obj/usr/src/sys/HOSTMASTER1  amd64

Write your code

main.c

#include 
#include 
#include "main_probes.h"

int main(void) {
        unsigned int count = 0;
        while(1) {
                sleep(1);
                SUPERTEST_MACHIN_START(&count);
                printf("count: %d\n", count++);
                SUPERTEST_MACHIN_DONE();
        }
}

main_probes.d

cat main_probes.d
provider supertest {
        probe machin__start(unsigned int *);
        probe machin__done();
};

Compile

dtrace -C -h -s main_probes.d
clang -c main.c
dtrace -G -s main_probes.d main.o
clang -lelf -o prog main_probes.o main.o

Use

Start the program

./prog
count: 0
count: 1
count: 2
count: 3
count: 4
...

Check that the probes are visible

dtrace -l | grep supertest
    4 supertest4056              prog                              main machin-done
    5 supertest4056              prog                              main machin-start

Use the probes

dtrace -n ':prog::machin-*'
dtrace: description ':prog::machin-*' matched 2 probes
dtrace: buffer size lowered to 2m
CPU     ID                    FUNCTION:NAME
  0      5                main:machin-start
  0      4                 main:machin-done
  1      5                main:machin-start
  1      4                 main:machin-done
  0      5                main:machin-start
  0      4                 main:machin-done
  1      5                main:machin-start
  1      4                 main:machin-done
  1      5                main:machin-start
  1      4                 main:machin-done

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