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

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)