So, we have basically rewritten the tornado patch idea using the C++17 string_view API (subset implemented in APT::StringView). This improved performance by about 10% on my test systems.

Here's the commit:

http://anonscm.debian.org/cgit/apt/apt.git/commit/?id=eff0c2...

also further improvement:

http://anonscm.debian.org/cgit/apt/apt.git/commit/?id=dd5927...

and finally, dropping strings out of StoreString(), so it's now almost entirely gone:

http://anonscm.debian.org/cgit/apt/apt.git/commit/?id=869700...