async_hooks: use typed array stack as fast path

- Communicate the current async stack length through a
  typed array field rather than a native binding method
- Add a new fixed-size `async_ids_fast_stack` typed array
  that contains the async ID stack up to a fixed limit.
  This increases performance noticeably, since most of the time
  the async ID stack will not be more than a handful of
  levels deep.
- Make the JS `pushAsyncIds()` and `popAsyncIds()` functions
  do the same thing as the native ones if the fast path
  is applicable.

Benchmarks:

    $ ./node benchmark/compare.js --new ./node --old ./node-master --runs 10 --filter next-tick process | Rscript benchmark/compare.R
    [00:03:25|% 100| 6/6 files | 20/20 runs | 1/1 configs]: Done
                                                   improvement confidence      p.value
     process/next-tick-breadth-args.js millions=4     19.72 %        *** 3.013913e-06
     process/next-tick-breadth.js millions=4          27.33 %        *** 5.847983e-11
     process/next-tick-depth-args.js millions=12      40.08 %        *** 1.237127e-13
     process/next-tick-depth.js millions=12           77.27 %        *** 1.413290e-11
     process/next-tick-exec-args.js millions=5        13.58 %        *** 1.245180e-07
     process/next-tick-exec.js millions=5             16.80 %        *** 2.961386e-07

PR-URL: https://github.com/nodejs/node/pull/17780
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/env.cc b/src/env.cc
index c3f42302ae..eb8cad15ed 100644
--- a/src/env.cc
+++ b/src/env.cc
@@ -403,4 +403,21 @@ void Environment::CollectUVExceptionInfo(v8::Local<v8::Value> object,
                              syscall, message, path, dest);
 }
 
+
+void Environment::AsyncHooks::grow_async_ids_stack() {
+  const uint32_t old_capacity = async_ids_stack_.Length() / 2;
+  const uint32_t new_capacity = old_capacity * 1.5;
+  AliasedBuffer<double, v8::Float64Array> new_buffer(
+      env()->isolate(), new_capacity * 2);
+
+  for (uint32_t i = 0; i < old_capacity * 2; ++i)
+    new_buffer[i] = async_ids_stack_[i];
+  async_ids_stack_ = std::move(new_buffer);
+
+  env()->async_hooks_binding()->Set(
+      env()->context(),
+      env()->async_ids_stack_string(),
+      async_ids_stack_.GetJSArray()).FromJust();
+}
+
 }  // namespace node