http: keep request option copies in fast mode

The options of every client request are copied several times: once
in ClientRequest to merge the URL and the options, once more to
build the options handed to the agent, and again in Agent#addRequest
(on every request, including keep-alive reuse) and createSocket to
merge in the agent options. Each copy was a `{ __proto__: null, ...}`
literal or an Object.assign() onto `{ __proto__: null }`. V8 creates
such an object in dictionary mode, and copying from a dictionary-mode
source takes the generic slow path, so every copy in the chain was
slow and fed a slow source into the next one.

Build each copy as an ordinary object literal and set its prototype
to null afterwards, which leaves a fast-mode object with a null
prototype and the same own properties in the same order. The same is
done for the copy of the options in the http and https Agent
constructors, which is the source of the agent options merged into
every request.

On a keep-alive client against a raw TCP responder (10 runs each,
medians, busy machine) this goes from 68.7k to 83.1k requests per
second and from 8.7 to 6.4 us of user CPU per request.

Assisted-by: claude:opus-5.5
Signed-off-by: Gürgün Dayıoğlu <hey@gurgun.day>

Author: gurgunday

lib/https.js

@@ -489,7 +489,7 @@ function Agent(options) {
   if (!(this instanceof Agent))
     return new Agent(options);
 
-  options = { __proto__: null, ...options };
+  options = ObjectSetPrototypeOf({ ...options }, null);
   validateOpenSSLEngineOptions(options);
   options.defaultPort ??= 443;
   options.protocol ??= 'https:';

lib/internal/http/agent.js

@@ -158,7 +158,7 @@ function Agent(options) {
 
   EventEmitter.call(this);
 
-  this.options = { __proto__: null, ...options };
+  this.options = ObjectSetPrototypeOf({ ...options }, null);
 
   this.defaultPort = this.options.defaultPort || 80;
   this.protocol = this.options.protocol || 'http:';
@@ -375,7 +375,7 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
   }
 
   // Here the agent options will override per-request options.
-  options = { __proto__: null, ...options, ...this.options };
+  options = ObjectSetPrototypeOf({ ...options, ...this.options }, null);
   if (options.socketPath)
     options.path = options.socketPath;
 
@@ -445,7 +445,7 @@ Agent.prototype.addRequest = function addRequest(req, options, port/* legacy */,
 
 Agent.prototype.createSocket = function createSocket(req, options, cb) {
   // Here the agent options will override per-request options.
-  options = { __proto__: null, ...options, ...this.options };
+  options = ObjectSetPrototypeOf({ ...options, ...this.options }, null);
   if (options.socketPath)
     options.path = options.socketPath;
 

lib/internal/http/client.js

@@ -26,7 +26,6 @@ const {
   Boolean,
   Error,
   NumberIsFinite,
-  ObjectAssign,
   ObjectDefineProperty,
   ObjectHasOwn,
   ObjectKeys,
@@ -363,7 +362,8 @@ function ClientRequest(input, options, cb) {
       pathIsFromURL = false;
     }
 
-    options = ObjectAssign({ __proto__: null }, input, options);
+    // Avoid creating a dictionary-mode object.
+    options = ObjectSetPrototypeOf({ ...input, ...options }, null);
   }
 
   // Propagate the user's highWaterMark to OutgoingMessage so that
@@ -411,7 +411,7 @@ function ClientRequest(input, options, cb) {
   const defaultPort = options.defaultPort ||
                     (this.agent?.defaultPort);
 
-  const optsWithoutSignal = { __proto__: null, ...options };
+  const optsWithoutSignal = ObjectSetPrototypeOf({ ...options }, null);
 
   const port = optsWithoutSignal.port = options.port || defaultPort || 80;
   const host = optsWithoutSignal.host = validateHost(options.hostname, 'hostname') ||