Sun Studio 12: Performance Analyzer

Synchronization Wait Tracing

Synchronization wait tracing is available only on Solaris platforms. The Collector collects synchronization delay events by tracing calls to the functions in the threads library,, or to the real time extensions library, The event-specific data consists of high-resolution timestamps for the request and the grant (beginning and end of the call that is traced), and the address of the synchronization object (the mutex lock being requested, for example). The thread and LWP IDs are the IDs at the time the data is recorded. The wait time is the difference between the request time and the grant time. Only events for which the wait time exceeds the specified threshold are recorded. The synchronization wait tracing data is recorded in the experiment at the time of the grant.

The LWP on which the waiting thread is scheduled cannot perform any other work until the event that caused the delay is completed. The time spent waiting appears both as Synchronization Wait Time and as User Lock Time. User Lock Time can be larger than Synchronization Wait Time because the synchronization delay threshold screens out delays of short duration.

The wait time is distorted by the overhead for data collection. The overhead is proportional to the number of events collected. You can minimize the fraction of the wait time spent in overhead by increasing the threshold for recording events.