Enhance interpretation of GLOO_SOCKET_IFNAME (#22978)
Summary:
With this change you can now list multiple interfaces separated by
comma. ProcessGroupGloo creates a single Gloo context for every device
in the list (a context represents a connection to every other
rank). For every collective that is called, it will select the context
in a round robin fashion. The number of worker threads responsible for
executing the collectives is set to be twice the number of devices.
If you have a single physical interface, and wish to employ increased
parallelism, you can also specify
`GLOO_SOCKET_IFNAME=eth0,eth0,eth0,eth0`. This makes ProcessGroupGloo
use 4 connections per rank, 4 I/O threads, and 8 worker threads
responsible for executing the collectives.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22978
ghstack-source-id: 87006270
Differential Revision: D16339962
fbshipit-source-id: 9aa1dc93d8e131c1714db349b0cbe57e9e7266f1
