ben-manes / caffeine / #5622

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Count the inserting access in SampledPolicy frequency

A node's frequency started at zero, counting only re-accesses after
insertion. The Hyperbolic paper (ATC'17, Fig 1 / Eq 1) defines an
item's priority as n_i divided by its time in cache, where n_i is the
request count since it entered -- the inserting access counts, so a
new item enters at high priority ("temporary immunity") and decays
toward its true popularity. Caffeine's zero-based frequency gave a
fresh entry a hyperbolic priority of 0.0, the lowest, so sampled
Hyperbolic evicted new arrivals first -- the exact inversion of the
paper.

Initialize frequency to 1 at insertion so it means "requests since
entering", matching the paper's n_i. This is order-preserving for the
LFU and MFU selections (a uniform +1 shift leaves argmin/argmax
unchanged), so only Hyperbolic's eviction decisions change; FIFO, LRU,
MRU, and RANDOM do not read frequency.

4143 of 4154 branches covered (99.74%)

8412 of 8413 relevant lines covered (99.99%)

1.0 hits per line