Sphinx parallel build (#38785)
Summary:
See https://www.sphinx-doc.org/en/master/man/sphinx-build.html#cmdoption-sphinx-build-j
> Distribute the build over N processes in parallel, to make building on multiprocessor machines more effective. Note that not all parts and not all builders of Sphinx can be parallelized. If auto argument is given, Sphinx uses the number of CPUs as N.
- Timing results
- Python doc build on a 40-core machine: 9:34 down to 1:29
- pytorch_cpp_doc_push: ~1h 10m down to 47m
- pytorch_python_doc_push: 34m down to 32m
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38785
Differential Revision: D21691991
Pulled By: zou3519
fbshipit-source-id: cfc5e8cd13414640f82edfd2ad1ce4d9c7afce12
