* Item structure was changed to work with slab, where its last field
is used to access key, value, and ascii prefix, respectively.
* Item structured was worked to have a smaller footprint. It was
reduced from 104 bytes to 72 bytes.
* Reclaimer was temporarily disabled.
* Global LRU was removed from the cache. Now LRU eviction is done
on a per-slab-class basis, whenever the slab allocator runs out of
slab pages.
* Fragmentation issue is naturally solved with the slab algorithm,
where slab classes have chunks of the same size.
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