> You mean there's an upper limit to performance benefits of increasing cache sizes. A cache is a latency-hiding device over a working set of unknown size. The

> You mean there's an upper limit to performance benefits of increasing cache sizes. A cache is a latency-hiding device over a working set of unknown size. The latency of the cache depends on its size. So picking a cache size embodies a huge set of unknowns (the programs that will be run, their working set sizes, latency and size of main and swap memories etc.). In any case, for a given workload you could draw up a graph of cache size (and implied cache latency) vs throughput / latency and see that there is a sweet spot (larger cache does not substantially increase performance, but rather degrades it, due to increased cache latency). Furthermore, when you do a shrink, you could put the implied performance gains into making a bigger cache of the same (absolute) latency, or making a cache of the same size with lower latency; the latter might be implicitly required since you now probably have a faster core that wants a cache with lower absolute latency.