| name | 0.1.3-understand-exponential_backoff |
| description | [0.1.3] Contention management strategy backing off exponentially after failed lock acquisition; reduces bus traffic an |
understand-exponential_backoff
CALL NUMBER: concurrency_synchronization_primitives_and_memor.exponential_backoff : deep_spinlock(9)
DEFINITION: Contention management strategy backing off exponentially after failed lock acquisition; reduces bus traffic and collision; common in spinlock and CAS-based algorithm implementations.
Invoke this skill to understand exponential_backoff down to its primitives. The RELATIVE ROOT below is the least-fixed-point closure of everything it bundles from — the full import cone, grouped by the lib each prim comes from. Projected from a prover-typed KB (MAP/SWI-Prolog consistency gate): every reference below resolves.
THE RELATIVE ROOT (the import cone, by lib)
from concurrency_synchronization_primitives_and_memor
- thundering_herd (d1): Pattern where many threads wake simultaneously from a blocking operation but only one can proceed; wasteful of resources; often avoided with wake-one semantics or phased awakening.
from deep_spinlock
- backoff_iteration (d1): Zero-based counter tracking how many consecutive failed lock acquisition attempts have occurred since last success.
- backoff_multiplier (d1): Scaling factor (commonly 2.0) that multiplies the current delay on each failed acquisition attempt to produce the next delay interval.
- base_delay (d1): Initial wait time in nanoseconds or microseconds before the first lock acquisition retry; the starting point of the exponential schedule.
- current_delay (d1): The computed wait interval for the current retry iteration; derived from base_delay multiplied by backoff_multiplier raised to the iteration count, then capped by delay_ceiling.
- delay_ceiling (d1): Upper bound cap on the computed delay; prevents unbounded growth of wait times when contention persists across many iterations.
- jitter (d1): Randomized variance introduced into the computed delay to decorrelate competing threads and mitigate thundering-herd synchronization on lock release.
- decorrelated_jitter (d2): Jitter strategy where each thread computes delay = random.uniform(min_delay, previous_delay * 3); history-dependent decorrelation reduces coordinated retry waves.
- equal_jitter (d2): Jitter strategy computing delay = base_delay / 2 + random.uniform(0, base_delay / 2); ensures wait never falls below half the nominal delay.
- full_jitter (d2): Jitter strategy selecting a uniform random value in the range [0, current_delay]; maximizes desynchronization at the cost of potentially very short waits.
CONSUMERS (what needs this)
spinlock
Projected from the concurrency synchronization primitives and memory models KB (155 concepts / 137 relations) — consistency-typed by MAP; the facet list after the colon IS the cross-lib dependency web.
(leaf — this is an actual skill.)
