doc: add design_notes document

I actually forgot we have the part where we yield a client at the
end of every HTTP/1.x request.  This hurts cache CPU cache locality,
but I bet there's other things in Ruby which destroy CPU cache
locality much more than this.

Hopefully we don't forget this stuff for HTTP/2, because concurrency
for that is so tricky with muliplexed connections!

0 files changed, 0 insertions, 0 deletions