We’ve observed cases where the eviction candidate queue is frequently empty or underfilled, particularly during update-only eviction WT-15538. Eviction walks are active but eviction makes little progress because too few candidates are queued.

Eviction intentionally queues only a percentage of potential candidates in order to reserve space for urgent eviction. This is counterproductive when the queue is often empty and eviction is already under pressure.

This ticket is to test a change for when eviction is operating in update-only mode and the candidate queue is consistently empty when topping up, allow eviction to queue more candidates.