pydrake: Reduce size occupied by modules

[EricCousineau-TRI]

At fdd7553, in the //:install tree, pydrake occupies 112MB of space out of 566MB. For comparison, libdrake.so occupies 26MB.

This amount should be reduced, either via #8433 or by reducing the overall module count.

Will increase priority if this starts to become a bottleneck.

EDIT (2019-03-23): Benchmarking stuff:

$ cd drake
$ git rev-parse --short HEAD
361223416
$ rm -rf ./build/py2
$ bazel run //bindings/pydrake:install -- ${PWD}/build/py2
$ find ./build/py2 -name '*.so*' | xargs du -hsc
...
114M    total

$ rm -rf ./build/py3
$ bazel run --config=python3 //bindings/pydrake:install -- ${PWD}/build/py3
$ find ./build/py3 -name '*.so*' | xargs du -hsc
...
121M    total

[jamiesnape]

Does not seem unreasonable to me. Backlog?

[EricCousineau-TRI]

Not yet, depending on what solution we want to take for #10408.

[jwnimmer-tri]

@EricCousineau-TRI could you re-check the object code sizes, now that #10350 has merged?

[jamiesnape]

Not yet, depending on what solution we want to take for #10408.

I don't think #10408 changes anything. 112MB of 556MB is not unreasonable, and to be honest ~224MB of ~668MB is equally not unreasonable.

[EricCousineau-TRI]

All sounds good; knocking down priority to backlog. Will still briefly check sizes, probably tomorrow though.

[jwnimmer-tri]

If we ever pick this up again, we should try https://github.com/google/bloaty, e.g.,

bloaty -C full -d segments,sections,shortsymbols,symbols $(find bazel-bin/bindings/pydrake -name \*.runfiles -prune -o -name _objs -prune -o -name \*.so -print)

[jamiesnape]

Aside: Running the aforementioned McBloatface on libdrake.so is kind of interesting too (drake::math::GrayCodeToInteger() comes in at almost 20% of the size of the binary on Mac, next highest is 3%).

[EricCousineau-TRI]

Posted a brief benchmark script to run from source, specific to these artifacts. Haven't used McBloatface, yet.

Briefly tried using namespace pydrake __attribute__((visibility("hidden"))), but that wasn't the easy fix - size is almost exactly the same :(

$ git diff
diff --git a/bindings/pydrake/pydrake_pybind.h b/bindings/pydrake/pydrake_pybind.h
index cdfa1b5d1..da87675be 100644
--- a/bindings/pydrake/pydrake_pybind.h
+++ b/bindings/pydrake/pydrake_pybind.h
@@ -7,7 +7,7 @@
 // for) these binding capabilities.
 
 namespace drake {
-namespace pydrake {
+namespace pydrake __attribute__((visibility("hidden"))) {
 
 /** @defgroup python_bindings Python Bindings
 @ingroup technical_notes

$ ... # Ran benchmark above for Python 3:
121M    total

[jwnimmer-tri]

For the record, this is a lot better now that I've been folding modules together. I would advise we finish that first (getting to the point where we only have two shared libraries -- libdrake.so + libpydrake.so), and only after that we could investigate hidden symbols or other linker optimizations within libpydrake.so.

[jwnimmer-tri]

The change in #20465 helped somewhat (5%). Ongoing module-folding is on deck to continue to improve.

Also #20296 will help a lot.