README.md

pythonprobes

Fire a static Dtrace probe from Python with the ability to pass arbitrary strings to Dtrace. Makes it possible to add static Dtrace probes to any Python project without knowing any C.

Install

Download, and run:

python setup.py install

Example

Save the following script to a file and set to have execute permissions.

#!/usr/sbin/dtrace -qs

/**
 Prints out the arguments passed from Python
*/

pythonprobes*:::pythonprobe
{
    printf("%s || ", copyinstr(arg0));
    printf("%s || ", copyinstr(arg1));
    printf("%s || ", copyinstr(arg2));
    printf("%s || ", copyinstr(arg3));
    printf("%s\n", copyinstr(arg4));
}

And then run the following in a Python shell:

import probe

It is important to import probe before running the D script as otherwise the Dtrace probe will not be installed when you run the D script.

Now run your Dtrace as root or a privileged user in another terminal.

./example.d

Run the following in your Python shell.

for i in xrange(6):
    probe.dtrace_probe(*[str(x) for x in xrange(i)])

And you should see the following output from the Dtrace script.

null || null || null || null || null
0 || null || null || null || null
0 || 1 || null || null || null
0 || 1 || 2 || null || null
0 || 1 || 2 || 3 || null
0 || 1 || 2 || 3 || 4

DTraceProfiler

Is a line level profiler for Python that utilizes the pythonprobes package above and DTrace to gather line level profiling statistics on a Python program.

Consider the following Python program:

from time import sleep

from profiler import DTraceProfiler

def tester():
    print "Hello"
    x = 1
    x = x + x + x
    print "Good Bye"
    sleep(1)

def main():
    for i in xrange(15):
        tester()

pr = DTraceProfiler()
pr.run("main()")

When run in conjunction with the following D script:

#!/usr/sbin/dtrace -qs

self uint64_t lasttime;

BEGIN{
    self->lasttime = 0;
}

pythonprobes*:::pythonprobe
/self->lasttime == 0/
{
    self->lasttime = walltimestamp;
}


pythonprobes*:::pythonprobe
/self->lasttime != 0/
{
   @[copyinstr(arg1), copyinstr(arg0)] = sum(walltimestamp - self->lasttime);
   self->lasttime = walltimestamp;
}

The following output is returned after pressing ctrl-c on the D script.

root@southside:~# ~robin/workspace/dprobes/examples/profiler.d 
^C

  1                                                   /var/tmp/test.py                                                  0
  1                                                   <string>                                                          0
  14                                                  /var/tmp/test.py                                                  0
  6                                                   /var/tmp/test.py                                                  0
  7                                                   /var/tmp/test.py                                                  0
  8                                                   /var/tmp/test.py                                                  0
  9                                                   /var/tmp/test.py                                                  0
  13                                                  /var/tmp/test.py                                            9919833
  10                                                  /var/tmp/test.py                                        15020029009
root@southside:~# 

We can see that the program spends around 15 seconds in line 10 of test.py which is what would be expected with this program. Line 10 for i in xrange(15): is the second hot spot.