perf(policy): avoid per-sample heap allocations in eviction sampling#490
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nishantmehta wants to merge 1 commit into
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perf(policy): avoid per-sample heap allocations in eviction sampling#490nishantmehta wants to merge 1 commit into
nishantmehta wants to merge 1 commit into
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fillSample built the eviction candidate pool as []*policyPair, allocating a new policyPair on the heap for every sampled key. This runs on the eviction path (every Set once the cache is full), so a write-heavy workload pays lfuSample (5) small allocations per eviction round. policyPair is a 16-byte value type (two integers) and the sample is only read (to find the minimum-hit victim) and swap-removed, never retained or mutated through the pointer. Storing the pairs by value in a caller-sized slice keeps the single backing-array allocation while removing all the per-element ones. BenchmarkSampledLFUFillSample: 80 B/op -> 0 B/op, 5 allocs/op -> 0 allocs/op, ~50% faster (79ns -> 39ns). Signed-off-by: Nishant Mehta <nishantmehta.n@gmail.com>
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What
sampledLFU.fillSamplebuilds the eviction candidate pool as[]*policyPair, allocating a freshpolicyPairon the heap for every sampled key. This runs on the eviction path — everySetonce the cache is full — so a write-heavy workload payslfuSample(5) small allocations per eviction round.policyPairis a 16-byte pure value type (two integers), and the sample is only read (to find the minimum-hit victim) and swap-removed — it is never retained or mutated through the pointer. Storing the pairs by value in the caller-sized slice keeps the single backing-array allocation while removing all the per-element ones.Benchmark
(
benchstat, n=10, p=0.000.)Testing
Full test suite passes, including
-race. No API or behavioral change.