I have recently been in need of a profiler for my favorite Common Lisp
implementation, [Clozure Common Lisp](http://ccl.clozure.com/), but sadly its
[mechanism for generating a Lisp image for use with oprofile](http://ccl.clozure.com/docs/ccl.html#using-the-linux-oprofile-system-level-profiler)
no longer works with recent versions of Linux/oprofile. [rme](http://www.thoughtstuff.com/)
explained it to me in {#ccl} on Freenode:

“_Recent kernels and perf versions are not fooled by our trick of making a heap
image look sort of like an ELF file. Also, they only consider mapped memory
from ELF files (and not just some random file, like a heap image) as a place
where functions can reside._”

That was disappointing, I had waited for the new Slackware release to get a
compatible version of libelf, after all. I also looked into the deterministic
profiler for CCL by Hans Huebner that lives in {contrib/}, but that one
bit-rotted, sadly.

#media Still from the 2009 movie “Moon”. The protagonist’s name is Sam as
well.#
sam.jpg

Still, my search was not in vain. rme sent me a very helpful
[paste](http://paste.lisp.org/display/319875), whose contents he described as
“a crude userland-based sampling profiler”. Here is how it works: it peeks into
the call stack of a running process repeatedly to find out which function is
being run, and counts how often it finds the process busy with a given
function. With the collected information it can then report an estimate of
where time is spent.

After having given some love to this tiny profiler’s report output, I figured
why not share it for others to use, and rme kindly agreed. Meet
[Sam](https://github.com/eugeneia/sam), it supports profiling forms as well as
running processes, and is reasonably well
[documented](http://mr.gy/software/sam/api.html). You can use it to profile
arbitrary forms like this:

#code#
CL-USER> (sam:profile ()
           (loop for i from 1 to 1e8 sum i))
39%  CCL::>-2  <no source>
19%  CCL::FIXNUM-SFLOAT-COMPARE  <no source>
15%  #<Anonymous Function #x30200B10843F>  <no source>
12%  SAM:CALL-WITH-SAMPLING  (defun call-with-sampling (fn ...
11%  CCL::INTEGER-DECODE-SHORT-FLOAT  <no source>
 5%  CCL::FIXNUM-DECODE-SHORT-FLOAT  <no source>
#

…or profile a different process:

#code#
CL-USER> (sam:profile-process (fourth (all-processes)) 1)
100%  CCL::FD-READ  <no source>
#

May the search engines index this, and spare others from repeating my search
(but not from reading about it.) I hope Sam can be of use to you, and let me
know if you find any bugs!