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by romange
1397 days ago
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I agree. This is why DashCache is designed to be very efficient in terms of CPU and memory, while providing very strong adaptive capabilities for mixed workloads. If think the most important part in this design is the realization that we do not need a global order in order to choose an entry to evict: other heuristics like LRU, LFU, frecency - they strive to provide a single number, a metric. Obviously this metric lies because a single number can not represent well both qualities like frequency and recency. DashCache, on the other hand, does not try to do it at all. Instead, it implicitly defines a partial order between entries in the same bucket or segment.... |
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This is a key insight many people miss. The optimal eviction is not computable, so any reasonable approximation will likely have a similar outcome. Given this, it makes sense to pick an approximation that facilitates other objectives, like computational performance.