SpinDelay
Short Description
SpinDelay tracks delays caused by spinlocks that are in a "sleep" state.
Detailed Description​
SpinDelay was added in PostgreSQL 16 to report and track delays caused by spinlocks that are in a "sleep" state.
In PostgreSQL, SpinDelay is used in its spinlock implementation. Spinlocks are lightweight locks used to protect small critical sections in shared memory. PostgreSQL’s s_lock.c includes spinlock code where the SpinDelay is applied. This mechanism helps to:
- Avoid excessive CPU consumption during spinlock contention.
- Provide fairer access to locks in highly concurrent environments by introducing small delays between retries.
Trade-offs
- Pro: For short waits, it can significantly reduce latency compared to blocking.
- Con: For long waits, spinning wastes CPU cycles and can degrade overall system performance. Systems must carefully balance spin-waiting and yielding/blocking.
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