Commits on Jun 8, 2018

1. napi: improve runtime performance of every napi fun call. …

   Added a new struct CallbackBundle to eliminate all
   GetInternalField() calls.
   
   The principle is to store all required data inside a C++ struct,
   and then store the pointer in the JavaScript object. Before this
   change, the required data are stored in the JavaScript object in
   3 or 4 seperate pointers. For every napi fun call, 3 of them
   have to be fetched out, which are 3 GetInternalField() calls;
   after this change, the C++ struct will be directly fetched out
   by using v8::External::Value(), which is faster.
   
   Profiling data show that GetInternalField() is slow.
   On an i7-4770K (3.50GHz) box, a C++ V8-binding fun call is 8 ns,
   before this change, napi fun call is 36 ns; after this change,
   napi fun call is 20 ns.
   
   The above data are measured using a modified benchmark in
   'benchmark/misc/function_call'. The modification adds an indicator
   of the average time of a "chatty" napi fun call (max 50M runs).
   This change will speed up chatty case 1.8x (overall), and will cut
   down the delay of napi mechanism to approx. 0.5x.
   
   Background: a simple C++ binding function (e.g. receiving little
   from JS, doing little and returning little to JS) is called
   'chatty' case for JS<-->C++ fun call routine.
   
   This improvement also applies to getter/setter fun calls.

   

   kenny-y committed Jun 8, 2018
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