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

[Adam Barth]

On Tue, Oct 9, 2012 at 12:17 PM, Antti Koivisto <koivisto at iki.fi> wrote:
> On Tue, Oct 9, 2012 at 10:02 PM, Adam Barth <abarth at 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.

Adam