stream: improve performance for sync write finishes

Improve performance and reduce memory usage when a writable stream
is written to with the same callback (which is the most common case)
and when the write operation finishes synchronously (which is also
often the case).

                                                         confidence improvement accuracy (*)    (**)   (***)
    streams/writable-manywrites.js sync='no' n=2000000                  0.99 %       ±3.20%  ±4.28%  ±5.61%
    streams/writable-manywrites.js sync='yes' n=2000000        ***    710.69 %      ±19.65% ±26.47% ±35.09%

Refs: https://github.com/nodejs/node/issues/18013
Refs: https://github.com/nodejs/node/issues/18367

PR-URL: https://github.com/nodejs/node/pull/30710
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/benchmark/streams/writable-manywrites.js b/benchmark/streams/writable-manywrites.js
index 6fcb07e849..0ed38d0357 100644
--- a/benchmark/streams/writable-manywrites.js
+++ b/benchmark/streams/writable-manywrites.js
@@ -4,14 +4,19 @@ const common = require('../common');
 const Writable = require('stream').Writable;
 
 const bench = common.createBenchmark(main, {
-  n: [2e6]
+  n: [2e6],
+  sync: ['yes', 'no']
 });
 
-function main({ n }) {
+function main({ n, sync }) {
   const b = Buffer.allocUnsafe(1024);
   const s = new Writable();
+  sync = sync === 'yes';
   s._write = function(chunk, encoding, cb) {
-    cb();
+    if (sync)
+      cb();
+    else
+      process.nextTick(cb);
   };
 
   bench.start();