worker: refactor stdio to improve performance

Signed-off-by: Matteo Collina <hello@matteocollina.com>
PR-URL: #56630
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: mcollina

lib/internal/worker.js

@@ -340,9 +340,11 @@ class Worker extends EventEmitter {
 {
 const{ stream, chunks }=message;
 constreadable=this[kParentSideStdio][stream];
-ArrayPrototypeForEach(chunks,({ chunk, encoding })=>{
+// This is a hot path, use a for(;;) loop
+for(leti=0;i<chunks.length;i++){
+const{ chunk, encoding }=chunks[i];
 readable.push(chunk,encoding);
-});
+}
 return;
 }
 casemessageTypes.STDIO_WANTS_MORE_DATA:

lib/internal/worker/io.js

@@ -1,9 +1,7 @@
 'use strict';
 
 const{
- ArrayPrototypeForEach,
- ArrayPrototypeMap,
- ArrayPrototypePush,
+ Array,
  FunctionPrototypeBind,
  FunctionPrototypeCall,
  ObjectAssign,
@@ -77,7 +75,7 @@ const kOnMessage = Symbol('kOnMessage');
 constkOnMessageError=Symbol('kOnMessageError');
 constkPort=Symbol('kPort');
 constkWaitingStreams=Symbol('kWaitingStreams');
-constkWritableCallbacks=Symbol('kWritableCallbacks');
+constkWritableCallback=Symbol('kWritableCallback');
 constkStartedReading=Symbol('kStartedReading');
 constkStdioWantsMoreDataCallback=Symbol('kStdioWantsMoreDataCallback');
 constkCurrentlyReceivingPorts=
@@ -282,20 +280,29 @@ class WritableWorkerStdio extends Writable {
 super({decodeStrings: false});
 this[kPort]=port;
 this[kName]=name;
-this[kWritableCallbacks]=[];
+this[kWritableCallback]=null;
 }
 
 _writev(chunks,cb){
+consttoSend=newArray(chunks.length);
+
+// We avoid .map() because it's a hot path
+for(leti=0;i<chunks.length;i++){
+const{ chunk, encoding }=chunks[i];
+toSend[i]={ chunk, encoding };
+}
+
 this[kPort].postMessage({
 type: messageTypes.STDIO_PAYLOAD,
 stream: this[kName],
-chunks: ArrayPrototypeMap(chunks,
-({ chunk, encoding })=>({ chunk, encoding })),
+chunks: toSend,
 });
 if(process._exiting){
 cb();
 }else{
-ArrayPrototypePush(this[kWritableCallbacks],cb);
+// Only one writev happens at any given time,
+// so we can safely overwrite the callback.
+this[kWritableCallback]=cb;
 if(this[kPort][kWaitingStreams]++===0)
 this[kPort].ref();
 }
@@ -311,11 +318,13 @@ class WritableWorkerStdio extends Writable {
 }
 
 [kStdioWantsMoreDataCallback](){
-constcbs=this[kWritableCallbacks];
-this[kWritableCallbacks]=[];
-ArrayPrototypeForEach(cbs,(cb)=>cb());
-if((this[kPort][kWaitingStreams]-=cbs.length)===0)
-this[kPort].unref();
+constcb=this[kWritableCallback];
+if(cb){
+this[kWritableCallback]=null;
+cb();
+if(--this[kPort][kWaitingStreams]===0)
+this[kPort].unref();
+}
 }
 }