[webkit-dev] Discussing bug 98539 - Refactor resource loading to allow for out-of-process loading and memory caching

[Geoffrey Garen]

> My guess is that frequency of hits on given cache items approximately follows a power law distribution, and therefore increasing cache size gives diminishing returns.

FWIW, a few years back I did some in-depth data gathering on this score using "real world" websites. I found that, for encoded data, hit rate in the cache increased exponentially as cache size increased up to ~4MB, increased linearly as cache size increased above ~4MB, and increased not at all as cache size increased above ~100MB (since all resources that were eligible for caching and not expired were already in the cache). My guess is that the inflection points in the graph have moved out to ~8MB or ~16MB in the past few years.

Note that these numbers do not correspond precisely to WebCore cache sizes, since the WebCore cache size includes both encoded and decoded data.

Of course, the precise hit rates you'll see depend on the content you're browsing, and it's possible to hand-craft content that shows benefits up to arbitrarily large cache sizes, or shows no benefits down to arbitrarily small cache sizes. 

Geoff