You are training an object detection model using a Cloud TPU v2.

 The trace in the question shows that the training time is taking longer than expected. This is likely due to the input function not being optimized. To decrease training time in a cost-efficient way, the best option is to rewrite the input function using parallel reads, parallel processing, and prefetch. This will allow the model to process the data more efficiently and decrease training time. References:

[Cloud TPU Performance Guide]

[Data input pipeline performance guide]