How many machines did my MR job used?

Hello,

I am running a Pig script which internally starts several jobs. For one of
the jobs that uses maximum no. of mappers reducers, I need to find out
how many machines it's running on which machines are those.

I looked around the JobTracker UI, but couldn't find this information. Is
it there somewhere? Is it in any of the logs?

Would appreciate any help on this. Thanks.