maxAcAllocationWatermark: Item is always allocated in topmost tier if at least this percentage of the AllocationClass is free.minAcAllocationWatermark: Item is always allocated in bottom tier if only this percent of the AllocationClass is free. If percentage of free AllocationClasses is betweenmaxAcAllocationWatermarkandminAcAllocationWatermark: then extra checks (described below) are performed to decide where to put the element.
By default, allocation will always be performed from the upper tier.
acTopTierEvictionWatermark: If there is less that this percent of free memory in topmost tier, cachelib will attempt to evict from top tier. This option takes precedence before allocationWatermarks.
Extra policies (used only when percentage of free AllocationClasses is between maxAcAllocationWatermark
and minAcAllocationWatermark)
sizeThresholdPolicy: If item is smaller than this value, always allocate it in upper tier.defaultTierChancePercentage: Change (0-100%) of allocating item in top tier
lruInsertionPointSpec: Can be set per tier when LRU2Q is used. Determines where new items are inserted. 0 = insert to hot queue, 1 = insert to warm queue, 2 = insert to cold queuemarkUsefulChance: Per-tier, determines chance of moving item to the head of LRU on access