The Controlled Logical Clock - a Global Time for Trace Based Software Monitoring of Parallel Applications in Workstation Clusters
SWD-Schlagwörter: Parallelrechner , Paralleler Prozess , Prozessüberwachung , Synchronisierung
Institut: Rechenzentrum der Universität (RUS)
Dokumentart: InProceedings (Aufsatz / Paper einer Konferenz etc.)
Kurzfassung auf Englisch: Event tracing and monitoring of parallel applications are difficult if each processor
has its own unsynchronized clock. A survey is given on several strategies to
generate a global time, and their limits are discussed. The controlled logical
clock is a new method based on Lamport''s logical clock and provides a method to
modify inexact timestamps of tracefiles. The new timestamps guarantee the clock
condition, i.e. that the receive event of a message has a later timestamp than
the send event. The cor-rected timestamps can also be used for performance
measurements with pairs of events in different processes. The controlled logical
clock is motivated and it is ana-lyzed in detail by computer simulations. No
additional protocol overhead is needed for the new method while tracing an application.
It can be implemented as a filter for trace-files or it can be integrated into
monitor tools for parallel applications.