Memory profiling the OCaml heap

The profiler offers specific support for displaying the memory footprint of the OCaml heap. This is how you can use it

Using Memtrace

• Install an OCaml switch that support statmemprof: until the 4.14.2 or after the 5.3

• Install memtrace and memtrace_viewer.

• Add the following line at the beginning of the program you want to profile Memtrace.trace_if_requested ();

• Recompile your program

• Add the following environment variable to your executable command: MEMTRACE=trace.ctf ./my_executable

• trace.ctf will be filled with data from the execution of the program and can be analysed with memtrace-viewer trace.ctf.

• Open your favorite web browser and go to localhost:8080

Using Statmemprof-emacs

This section is legacy and might not work any more with recent OCaml versions.

• Install an OCaml switch with the statmemprof patch: 4.04.2+statistical-memprof or 4.06.0+statistical-memprof

• Install statmemprof-emacs.

• Enable loading statmemprof into the node.

  Add the statmemprof-emacs package as a dependency to the main package, and add let () = Statmemprof_emacs.start 1E-4 30 5 to the node_main.ml file.

  Arguments:

  • sampling_rate is the sampling rate of the profiler. Good value: 1e-4.

  • callstack_size is the size of the fragment of the call stack which is captured for each sampled allocation.

  • min_sample_print is the minimum number of samples under which the location of an allocation is not displayed.

• Load sturgeon into emacs, by adding this to your .emacs:

(let ((opam-share (ignore-errors (car (process-lines "opam" "config" "var" "share")))))
  (when (and opam-share (file-directory-p opam-share))
  (add-to-list 'load-path (expand-file-name "emacs/site-lisp" opam-share))))

(require 'sturgeon)

• Launch the node then connect to it with sturgeon.

  If the process is launched with pid 1234 then

  M-x sturgeon-connect octez-nodememprof.1234.sturgeon
  

  (tab-completion works for finding the socket name)