[Martin Mathieson <martin.r.mathieson@xxxxxxxxxxxxxx>]

PS I suspect some new heuristic dissector has been introduced, since none of the other changes from 1.8 to trunk are likely to have such a significant performance impact.

I haven't checked to see when it was last changed, but I noticed a while back that SIP and HTTP were both pretty expensive.  They look for a complete line, which for binary data, can be really far into the frame.  I changed SIP and added https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=8822 for HTTP (with patch) as I don't know HTTP all that well.

Martin