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In computer science, a lock convoy is a performance problem that can occur when using locks for concurrency control in a multithreaded application.
A lock convoy occurs when multiple threads of equal priority contend repeatedly for the same lock. Unlike deadlock and livelock situations, the threads in a lock convoy do progress; however, each time a thread attempts to acquire the lock and fails, it relinquishes the remainder of its scheduling quantum and forces a context switch. The overhead of repeated context switches and underutilization of scheduling quanta degrade overall performance.
Lock convoys often occur when concurrency control primitives such as locks serialize access to a commonly used resource, such as a memory heap or a thread pool. They can sometimes be addressed by using non-locking alternatives such as lock-free algorithms or by altering the relative priorities of the contending threads.
See also
References
- Silberschatz, Abraham (2013). Operating System Concepts. John Wiley & Sons Inc. ISBN 978-1118129388.
- Blasgen, Mike; Gray, Jim; Mitoma, Mike; Blasgen, Mike; Mitoma, Like (1979). "The convoy phenomenon". Operating Systems Review. 13 (2): 20–25. CiteSeerX 10.1.1.646.921. doi:10.1145/850657.850659. S2CID 40305779.