Alright, use term_to_binary() for opaque/sexp-style encoding, only 15x slower.

machi_flu1_test: timing_pb_encoding_test_... speed factor=15.12 [2.678 s] ok

src/machi_pb_wrap.erl

@@ -67,7 +67,7 @@ conv_to_p_srvr(#mpb_p_srvr{name=Name,
             proto_mod=to_atom(ProtoMod),
             address=to_list(Address),
             port=to_integer(Port),
-            props=dec_sexp(to_list(Props))}.
+            props=dec_sexp(Props)}.
 
 enc_projection_v1(P) ->
     %% Awww, flatten it here
@@ -282,15 +282,10 @@ unmake_projection_resp(#mpb_ll_response{proj_la=#mpb_ll_listallprojectionsresp{
 %%%%%%%%%%%%%%%%%%%
 
 enc_sexp(T) ->
-    lists:flatten(io_lib:format("~w.", [T])).
+    term_to_binary(T).
 
 dec_sexp(Bin) when is_binary(Bin) ->
-    dec_sexp(binary_to_list(Bin));
-dec_sexp(String) when is_list(String) ->
-    {ok,Tks,_} = erl_scan:string(String),
-    {ok,E} = erl_parse:parse_exprs(Tks),
-    {value,Funs,_} = erl_eval:exprs(E,[]),
-    Funs.
+    binary_to_term(Bin).
 
 enc_optional_sexp(undefined) ->
     undefined;

test/machi_flu1_test.erl

@@ -230,7 +230,7 @@ timing_pb_encoding_test2() ->
                     ZZ = machi_pb:decode_mpb_ll_request(Bin),
                     _ = machi_pb_wrap:unmake_projection_req(ZZ)
             end,
-    XX = lists:seq(1,30*1000),
+    XX = lists:seq(1,70*1000),
     erlang:garbage_collect(),
     RUN1 = timer:tc(fun() -> begin [_ = DoIt1() || _ <- XX], ok end end),
     erlang:garbage_collect(),