Motivation for features / changes

As TPU pod is provided to cloud TPU users, we need to tool to provide a global visualization of the performance of each core, as well as the communication across the cores for your system.

Technical description of changes

The pod viewer UI shows:

• A step slider, which allows you to select which step you want to dive into.
• A topology graph, which interactively visualizes your TPU core in the whole TPU system.
• A step breakdown chart, which visualizes a breakdown of a step for all cores. This can be used to track where the bottleneck of the system is and whether there is a particular core slows down the system.
• A chart showing the latency of all the send-recv channels.
• A chart showing the latency of all-reduce ops.
• Communication links, which visualizes the send and recv channels in the topology graph. A channel details card also shows up on the right, providing detailed information of the channel, such as size of data transferred, latency and bandwidth.

Screenshots of UI changes

Detailed steps to verify changes work correctly (as executed by you)

bazel run tensorboard/plugins/profile:profile_demo
bazel run tensorboard:tensorboard -- --logdir=/tmp/profile_demo