Currently pmcstat cannot track thread IDs:
# ps -auxwwH -O lwp,comm | grep init
root 1 0.0 0.0 9476 248 - SLs 25Nov15 0:01.03 /sbin/init -- 1 100002 init - SLs 0:01.03 /sbin/init --
this is of course pid 1, but thread id 100002
# pmcstat -t 100002 -P unhalted-cycles -O /dev/null
pmcstat: ERROR: No processes were attached to.
When debugging multithreaded applications it can be beneficial to focus on specific threads, if different threads are performing different types of tasks.
This looks to now be supported by pmcstat -i lwp, please confirm that this works for you.