On Tue, Oct 9, 2012 at 1:31 PM, Maciej Stachowiak <m...@apple.com> wrote: > On Oct 9, 2012, at 1:24 PM, Adam Barth <aba...@webkit.org> wrote: >> On Tue, Oct 9, 2012 at 12:17 PM, Antti Koivisto <koivi...@iki.fi> wrote: >>> On Tue, Oct 9, 2012 at 10:02 PM, Adam Barth <aba...@webkit.org> wrote: >>>> This is interesting data, but it seems to be related to whether we >>>> should make the MemoryCache content addressable rather than whether we >>>> should use shared memory to back the MemoryCache when there are >>>> multiple WebProcesses. >>> >>> It is relevant when considering if and how to share cache data between >>> processes. It is also interesting in single process case. Brady's >>> refactoring should be helpful for both scenarios. >> >> Content-addressable caches are quite interesting. There are a couple >> benefits you could hope to achieve: >> >> 1) Reduced memory usage by deduping cached values. The data you >> mentioned seems mostly about this benefit. >> >> 2) Reduced latency by finding increasing the cache hit rate for >> duplicated entries. This one is trickier without cooperation from the >> server because you don't know the hash of the resource until you've >> already received it. >> >> We've had a couple of customers ask about (2), but there are some >> tricky security problems because you end up leaking the identity of >> cross-origin resources in the timing channel. Aiming for (1) also >> carries some of that risk because you'll leak the identity of >> cross-origin resources in the cache eviction channel (which can be >> probed with timing or network traffic), but it's likely not as big a >> problem. > > We're mainly interested in (1), with the corollary of greater cache > effectiveness at equivalent total cache size (so you can think of the benefit > as an indirect speed win rather than as just a memory win).
That raises the question of what the cache-size to hit-rate curve looks like. I don't think that's something we've ever measured for the MemoryCache, but it would be interesting to know, for example, whether increasing the cache size by 4% increases the cache hit rate by more or less than 4%. Adam _______________________________________________ webkit-dev mailing list webkit-dev@lists.webkit.org http://lists.webkit.org/mailman/listinfo/webkit-dev
