Performance and threaded applications
Job-level performance counters are updated by all the threads in a job.
The presence of multiple active threads can affect the accuracy of both general system counters and performance monitor specific transaction boundary counters. Data loss might occur as there is no automatic synchronization for these counters.
The initial thread performance information is a combination of thread and job-scoped data. Derived information that involves both thread and job-scoped data is not valid unless you total the thread-scoped data across all threads.