Lock convoy

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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.[1][2] 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.


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References[edit]

  1. ^ Silberschatz, Abraham (2013). Operating System Concepts. John Wiley & Sons Inc. ISBN 1118129385.
  2. ^ Blasgen, Mike; Gray, Jim; Mitoma, Mike; Blasgen, Mike; Mitoma, Like (1979). "The convoy phenomenon". Operating Systems Review.