perf: Optimize Header Validation

[PandaWorker]

The current implementation of header validation in the codebase uses Uint8Array to store character validity maps for HTTP tokens, URIs, and header values. While this approach works, it can be further optimized using bitmasking to reduce memory usage and improve performance.

undici/lib/core/util.js

Line 733 in e1496cf

function isValidHTTPToken (characters) {

const TOKEN_MAP = new Uint8Array([
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0,
	0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
]);

const URI_MAP = new Uint8Array([
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
]);

const HEADER_VALUE_MAP = new Uint8Array([
	0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
]);


export function isHTTPToken(c: number) {
	return c < 256 && TOKEN_MAP[c] === 1;
}

export function isHeaderValueToken(c: number) {
	return c < 256 && HEADER_VALUE_MAP[c] === 1;
}

export function isURIToken(c: number) {
	return c < 256 && URI_MAP[c] === 1;
}

export function isValidHeaderName(name: string) {
	for (let i = 0, len = name.length; i < len; i++) {
		if (!isHTTPToken(name.charCodeAt(i))) return false;
	}
	return true;
}

export function isValidHeaderValue(value: string) {
	for (let i = 0, len = value.length; i < len; i++) {
		if (!isHeaderValueToken(value.charCodeAt(i))) return false;
	}
	return true;
}

// undici 
const headerCharRegex = /[^\t\x20-\x7e\x80-\xff]/;

export function isValidHeaderValue2(characters: string): boolean {
	return !headerCharRegex.test(characters);
}

export function isTokenCharCode(c: number) {
	switch (c) {
		case 0x22:
		case 0x28:
		case 0x29:
		case 0x2c:
		case 0x2f:
		case 0x3a:
		case 0x3b:
		case 0x3c:
		case 0x3d:
		case 0x3e:
		case 0x3f:
		case 0x40:
		case 0x5b:
		case 0x5c:
		case 0x5d:
		case 0x7b:
		case 0x7d:
			// DQUOTE and "(),/:;<=>?@[\]{}"
			return false;
		default:
			// VCHAR %x21-7E
			return c >= 0x21 && c <= 0x7e;
	}
}

export function isValidHTTPToken(characters: string) {
	for (let i = 0; i < characters.length; ++i) {
		if (!isTokenCharCode(characters.charCodeAt(i))) {
			return false;
		}
	}
	return true;
}

Benchmarks

import * as utils from './constants.ts';

async function bench() {
	const { bench, run, summary } = await import('mitata');

	summary(() => {
		bench('isValidHeaderValue one char', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderValue(String.fromCharCode(index));
			}
		});

		bench('undici.isValidHeaderValue one char', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderValue2(String.fromCharCode(index));
			}
		});
	});

	summary(() => {
		bench('isValidHeaderValue', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderValue('accessToken=HFVTGWBNJNMDJNDJNDHBDHJDD123');
			}
		});

		bench('undici.isValidHeaderValue (re)', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderValue2('accessToken=HFVTGWBNJNMDJNDJNDHBDHJDD123');
			}
		});
	});


	summary(() => {
		bench('isHTTPToken', () => {
			for (let index = 0; index < 512; index++) {
				utils.isHTTPToken(index);
			}
		});

		bench('undici.isTokenCharCode', () => {
			for (let index = 0; index < 512; index++) {
				utils.isTokenCharCode(index);
			}
		});
	});

	summary(() => {
		bench('isValidHeaderName', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderName('X-Authorization-User-Id');
			}
		});

		bench('undici.isValidHTTPToken', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHTTPToken('X-Authorization-User-Id');
			}
		});
	});

	summary(() => {
		bench('isValidHeaderName invalid', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHeaderName('X-Authorization-User\n-Id');
			}
		});

		bench('undici.isValidHTTPToken invalid', () => {
			for (let index = 0; index < 512; index++) {
				utils.isValidHTTPToken('X-Authorization-User\n-Id');
			}
		});
	});

	for (let index = 0; index < 256; index++) {
		const char = String.fromCharCode(index);
		const [a, b] = [utils.isValidHeaderName(char), utils.isValidHTTPToken(char)];
		const [c, d] = [utils.isValidHeaderValue(char), utils.isValidHeaderValue2(char)];

		if ((a !== b) || (c !== d)) {
			console.warn({ index, char, a, b, c, d});
		}
	}

	run();
}

bench();

Results

clk: ~3.04 GHz
cpu: Apple M1 Max
runtime: node 22.12.0 (arm64-darwin)

benchmark                   avg (min … max) p75   p99    (min … top 1%)
------------------------------------------- -------------------------------
isValidHeaderValue one char    1.34 µs/iter   1.38 µs    ▄        █  ▂     
                        (1.26 µs … 1.48 µs)   1.43 µs ▅█▅█▅▅▂▁▁▂▁▂█▅██▅▂▁▂▂
undici.isValidHeaderValue ..   7.40 µs/iter   7.33 µs ▂█▂                  
                        (7.26 µs … 8.19 µs)   7.82 µs ███▇▁▄▁▁▁▁▁▁▁▄▁▁▁▁▁▁▄

summary
  isValidHeaderValue one char
   5.53x faster than undici.isValidHeaderValue one char

------------------------------------------- -------------------------------
isValidHeaderValue            19.84 µs/iter  20.16 µs  █                 █ 
                      (19.41 µs … 20.27 µs)  20.20 µs ▆█▁▆▁▁▁▁▁▁▁▁▆▆▁▁▁▁▁█▆
undici.isValidHeaderValue ..  20.48 µs/iter  20.44 µs  █                   
                      (20.36 µs … 21.11 µs)  20.70 µs ▅██▅▁▅▁▁▅▁▁▁▁▁▁▁▁▁▁▁▅

summary
  isValidHeaderValue
   1.03x faster than undici.isValidHeaderValue (re)

------------------------------------------- -------------------------------
isHTTPToken                  350.50 ns/iter 373.16 ns                    █ 
                    (182.86 ns … 389.65 ns) 381.80 ns ▃▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█▂
undici.isTokenCharCode       732.03 ns/iter 747.38 ns              █       
                    (676.33 ns … 796.38 ns) 786.35 ns ▅▂▁▁▁▁▁▁▁▁▁▁▁█▂▁▁▁▁▁▁

summary
  isHTTPToken
   2.09x faster than undici.isTokenCharCode

------------------------------------------- -------------------------------
isValidHeaderName             13.53 µs/iter  14.96 µs ▇             █      
                      (11.21 µs … 68.92 µs)  16.46 µs █▂▂▁▁▁▁▁▁▁▁▁▁▁█▂▃▁▂▁▁
undici.isValidHTTPToken       22.95 µs/iter  23.04 µs █ ▄                  
                      (21.96 µs … 83.75 µs)  31.96 µs █▂█▃▃▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁

summary
  isValidHeaderName
   1.7x faster than undici.isValidHTTPToken

------------------------------------------- -------------------------------
isValidHeaderName invalid     10.34 µs/iter  10.41 µs █ █                  
                      (10.18 µs … 10.53 µs)  10.51 µs █▁█▁▁▁██▁▁▁▁███▁▁▁█▁█
undici.isValidHTTPToken in..  20.10 µs/iter  20.36 µs  ▃                  █
                      (19.62 µs … 20.82 µs)  20.37 µs ▆█▁▁▆▁▁▁▁▁▆▁▁▁▆▆▁▁▆▁█

summary
  isValidHeaderName invalid
   1.94x faster than undici.isValidHTTPToken invalid

[PandaWorker]

Regular expressions start winning after about 20 characters, so you can use different implementations based on the number of characters.

export function isValidHeaderValue(value: string) {
	for (let i = 0, len = value.length; i < len; i++) {
		if (!isHeaderValueToken(value.charCodeAt(i))) return false;
	}
	return true;
}

export function isValidHeaderValueOptimized(value: string){
	return value.length >= 20 ? isValidHeaderValue2(value) : isValidHeaderValue(value);
}

// undici 
const headerCharRegex = /[^\t\x20-\x7e\x80-\xff]/;

export function isValidHeaderValue2(characters: string): boolean {
	return !headerCharRegex.test(characters);
}

import { bench, compact, lineplot, run } from 'mitata';
import * as utils from './constants.ts'; //

async function benchmark() {

	lineplot(() => {
		compact(() => {
			bench('isValidHeaderValue($size)', function* (state) {
				const size = state.get('size');
				yield () => utils.isValidHeaderValue('a'.repeat(size));
			}).range('size', 1, 512, 2);
	
			bench('isValidHeaderValue2($size)', function* (state) {
				const size = state.get('size');
	
				yield () => utils.isValidHeaderValue2('a'.repeat(size));
			}).range('size', 1, 512, 2).highlight('green');

			bench('isValidHeaderValueOp($size)', function* (state) {
				const size = state.get('size');
	
				yield () => utils.isValidHeaderValueOptimized('a'.repeat(size));
			}).range('size', 1, 512, 2).highlight('blue');
		});
	});

	run();
}

benchmark();

clk: ~2.98 GHz
cpu: Apple M1 Max
runtime: node 22.12.0 (arm64-darwin)

benchmark                   avg (min … max) p75   p99    (min … top 1%)
------------------------------------------- -------------------------------
isValidHeaderValue(1)          6.44 ns/iter   6.09 ns  13.39 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue(2)         13.48 ns/iter  13.01 ns  36.89 ns █▁▁▁▁▁▁▁▁▁▁
isValidHeaderValue(4)         22.71 ns/iter  22.59 ns  42.43 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue(8)         35.61 ns/iter  35.10 ns  55.83 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue(16)        89.79 ns/iter  89.51 ns 111.66 ns █▄▁▁▁▁▁▁▁▁▁
isValidHeaderValue(32)       148.24 ns/iter 146.65 ns 180.44 ns ▂▇█▂▁▁▁▁▁▁▁
isValidHeaderValue(64)       244.00 ns/iter 244.31 ns 272.60 ns ▂▁▁▃█▁▁▁▁▁▁
isValidHeaderValue(128)      430.87 ns/iter 434.69 ns 489.22 ns ▂▁▁▁█▂▂▁▁▁▁
isValidHeaderValue(256)      784.24 ns/iter 801.97 ns 831.61 ns ▃▂▁▁▁▁▁█▁▂▁
isValidHeaderValue(512)        1.48 µs/iter   1.54 µs   1.58 µs ▇▃▂▁▁▁▁▁█▂▂
isValidHeaderValue2(1)        14.00 ns/iter  13.80 ns  18.68 ns █▁▁▁▁▁▁▁▁▁▁
isValidHeaderValue2(2)        19.95 ns/iter  19.53 ns  25.35 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue2(4)        27.76 ns/iter  27.76 ns  47.04 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue2(8)        37.00 ns/iter  36.50 ns  57.35 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValue2(16)       97.36 ns/iter  96.73 ns 120.33 ns █▃▁▁▁▁▁▁▁▁▁
isValidHeaderValue2(32)      119.66 ns/iter 120.23 ns 162.14 ns █▅▂▁▁▁▁▁▁▁▁
isValidHeaderValue2(64)      163.11 ns/iter 163.44 ns 194.48 ns █▃▂▁▁▁▁▁▁▁▁
isValidHeaderValue2(128)     229.44 ns/iter 226.66 ns 311.33 ns █▄▂▁▁▁▁▁▁▁▁
isValidHeaderValue2(256)     337.58 ns/iter 339.38 ns 369.10 ns ▄█▅▃▂▁▂▂▂▁▁
isValidHeaderValue2(512)     548.84 ns/iter 551.52 ns 575.91 ns ▅█▄▂▁▁▂▃▂▁▁
isValidHeaderValueOp(1)        6.12 ns/iter   6.06 ns   7.03 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValueOp(2)       13.20 ns/iter  12.95 ns  17.33 ns █▂▁▁▁▁▁▁▁▁▁
isValidHeaderValueOp(4)       22.80 ns/iter  22.42 ns  42.80 ns █▁▁▁▁▁▁▁▁▁▁
isValidHeaderValueOp(8)       37.17 ns/iter  37.28 ns  67.53 ns █▄▁▁▁▁▁▁▁▁▁
isValidHeaderValueOp(16)      93.46 ns/iter  93.99 ns 131.66 ns ██▃▂▁▁▁▁▁▁▁
isValidHeaderValueOp(32)     118.41 ns/iter 118.92 ns 147.88 ns █▄▂▁▁▁▁▁▁▁▁
isValidHeaderValueOp(64)     166.91 ns/iter 164.30 ns 235.86 ns █▃▂▁▁▁▁▁▁▁▁
isValidHeaderValueOp(128)    227.26 ns/iter 229.28 ns 268.29 ns ▆▅█▃▂▁▁▁▁▁▁
isValidHeaderValueOp(256)    336.57 ns/iter 340.00 ns 376.96 ns █▅▃▂▂▂▁▁▁▁▁
isValidHeaderValueOp(512)    560.46 ns/iter 569.84 ns 615.56 ns ██▄▇▅▃▂▂▂▁▁

                             ┌                                            ┐
   isValidHeaderValue($size)                                             ⡜ 1.48 µs
  isValidHeaderValue2($size)                                            ⢰⠁
 isValidHeaderValueOp($size)                                           ⢀⠇ 
                                                                       ⡜  
                                                                      ⢰⠁  
                                                                     ⢀⠇   
                                                                     ⡜    
                                                                    ⡰⠁    
                                                                   ⡰⠁     
                                                                  ⡜      ⢀
                                                                ⢀⠎     ⢀⡴⠋
                                                              ⢀⡠⠊    ⢀⠔⠋  
                                                            ⣀⠔⠁   ⣀⡤⠖⠁    
                                                        ⣀⡠⠔⠊⣀⣀⣤⠴⠖⠋⠁       
                                                 ⣀⣀⣤⠤⠶⠶⠝⠒⠒⠉⠉⠁             
                              ⣀⣀⣀⣤⣤⣤⣤⡤⠤⠤⠤⠤⠤⠤⠤⠔⠒⠊⠉                          6.12 ns
                             └                                            ┘

[mcollina]

Wow, this is a comprehensive anaylisis. Would you like to send a PR? We'd indeed need to use both approaches, one for short headers and one for long ones.

How did you come by this improvement? Did you find that header validation was a bottleneck for a specific case in Undici? Does this improvement speed up our benchmarks?

[ronag]

I would prefer to just use regular expressions. Seems like a good balance between performance and maintainability.

[PandaWorker]

@mcollina , In applications where a large number of network requests are required, it is important that they are as productive as possible, not only without headers, but also with headers. I measured queries without headers and with headers in profiling mode.

Also, such services often have the same requests, and it would be good to do something like a PreparedRequest that will create a structure that does not require further validation of headers and transformation of the request body.

Here are the functions that need to be reviewed for optimization:
*processHeader /undici/lib/core/request.js:322:24
*Request /undici/lib/core/request.js:31:15
*parseHeaders /undici/lib/core/util.js:408:23
RegExp: [^\t\x20-\x7e\x80-\xff]
*resumeH1 /undici/lib/dispatcher/client-h1.js:958:19

// @ts-nocheck
import { Agent, request } from 'undici';

const dispatcher = new Agent({ connections: 100 });

const header = new Headers();
header.set(`x-authorization-user-id-1`, `a`.repeat(10 * 20 * 25));

const headers = new Headers();
for (let index = 0; index < 20; index++) {
	headers.set(`x-authorization-user-id-${index}`, `a`.repeat(10));
}

const optionsWithHeaders = {
	method: 'GET',
	dispatcher,
	headers: headers,
};

const optionsWithOneHeader = {
	method: 'GET',
	dispatcher,
	headers: header,
};

const optionsWithoutHeaders = {
	method: 'GET',
	dispatcher,
};

let rpc = 0;
const rpcInterval = setInterval(() => {
	const curr = rpc;
	rpc = 0;

	curr > 0 && console.log(`rps:`, curr);
}, 1000);

async function worker(options) {
	const resp = await request('http://localhost:8000', options);
	await resp.body.dump();
	rpc += 1;
}

async function main() {
	{
		const start = performance.now();
		const tasks = Array.from({ length: 1e6 }, () => worker(optionsWithOneHeader));
		await Promise.all(tasks);
		const end = performance.now();

		console.log(`with one header:`, (end - start).toFixed(2)); // with one header: 23557.95
	}

	{
		const start = performance.now();
		const tasks = Array.from({ length: 1e6 }, () => worker(optionsWithHeaders));
		await Promise.all(tasks);
		const end = performance.now();

		console.log(`with Headers:`, (end-start).toFixed(2)); // with Headers: 20957.07
	}

	{
		const start = performance.now();
		const tasks = Array.from({ length: 1e6 }, () => worker(optionsWithoutHeaders));
		await Promise.all(tasks);
		const end = performance.now();

		console.log(`without Headers:`, (end-start).toFixed(2)); // without Headers: 17486.71
	}
}

main().then(() => clearInterval(rpcInterval));

one header (5000 len)

 [JavaScript]:
   ticks  total  nonlib   name
   2807   14.5%   14.5%  RegExp: [^\t\x20-\x7e\x80-\xff]
    277    1.4%    1.4%  JS: *wasm-function[20]
    269    1.4%    1.4%  Builtin: KeyedLoadIC_Megamorphic
    195    1.0%    1.0%  JS: *parseHeaders /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/util.js:408:23
    158    0.8%    0.8%  Builtin: LoadIC
    133    0.7%    0.7%  JS: *resumeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:958:19
    133    0.7%    0.7%  JS: *_resume /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:533:18
    125    0.6%    0.6%  Builtin: CreateTypedArray
    105    0.5%    0.5%  Builtin: RecordWriteSaveFP
    101    0.5%    0.5%  JS: *processTicksAndRejections node:internal/process/task_queues:72:35
    100    0.5%    0.5%  JS: *Request /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:31:15
     91    0.5%    0.5%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool.js:75:20
     81    0.4%    0.4%  Builtin: RunMicrotasks
     76    0.4%    0.4%  Builtin: KeyedStoreIC_Megamorphic
     62    0.3%    0.3%  JS: *Readable.read node:internal/streams/readable:647:35
     61    0.3%    0.3%  JS: *nextTick node:internal/process/task_queues:113:18
     60    0.3%    0.3%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:279:15
     59    0.3%    0.3%  JS: *dump /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/api/readable.js:258:14
     57    0.3%    0.3%  JS: *Readable.on node:internal/streams/readable:1127:33
     56    0.3%    0.3%  JS: *wasm_on_header_value /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:127:29
     54    0.3%    0.3%  JS: *processHeader /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:322:24
     52    0.3%    0.3%  Builtin: LoadIC_Megamorphic
     51    0.3%    0.3%  JS: *writeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:998:18
     44    0.2%    0.2%  RegExp: [^\u0021-\u00ff]
     43    0.2%    0.2%  JS: *onHeaders /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:236:13
     41    0.2%    0.2%  JS: *worker file:///http/bench/1.ts:1:711
     38    0.2%    0.2%  JS: *onDrain /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool-base.js:31:39

20 headers with 10 len

[JavaScript]:
   ticks  total  nonlib   name
    915    4.9%    8.0%  JS: *processHeader /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:322:24
    304    1.6%    2.7%  JS: *wasm-function[20]
    254    1.4%    2.2%  JS: *Request /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:31:15
    197    1.1%    1.7%  JS: *parseHeaders /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/util.js:408:23
    151    0.8%    1.3%  RegExp: [^\t\x20-\x7e\x80-\xff]
    119    0.6%    1.0%  JS: *resumeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:958:19
    110    0.6%    1.0%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool.js:75:20
    108    0.6%    0.9%  JS: *processTicksAndRejections node:internal/process/task_queues:72:35
    106    0.6%    0.9%  JS: *writeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:998:18
     97    0.5%    0.8%  JS: *_resume /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:533:18
     89    0.5%    0.8%  JS: *wasm_on_header_value /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:127:29
     72    0.4%    0.6%  RegExp: [^\u0021-\u00ff]
     72    0.4%    0.6%  JS: *Readable.read node:internal/streams/readable:647:35
     69    0.4%    0.6%  JS: *nextTick node:internal/process/task_queues:113:18
     54    0.3%    0.5%  JS: *dump /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/api/readable.js:258:14
     52    0.3%    0.5%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:279:15
     50    0.3%    0.4%  JS: *runInAsyncScope node:async_hooks:204:18
     48    0.3%    0.4%  JS: *wasm_on_header_field /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:116:29
     43    0.2%    0.4%  JS: *worker file:///http/bench/1.ts:1:555
     42    0.2%    0.4%  JS: *Readable.on node:internal/streams/readable:1127:33
     37    0.2%    0.3%  JS: *emitReadable node:internal/streams/readable:819:22
     37    0.2%    0.3%  JS: *Readable.push node:internal/streams/readable:387:35
     36    0.2%    0.3%  JS: *wasm_on_message_complete /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:158:33
     31    0.2%    0.3%  JS: *emit node:events:471:44
     30    0.2%    0.3%  JS: *Readable node:internal/streams/readable:320:18
     29    0.2%    0.3%  JS: wasm-to-js
     29    0.2%    0.3%  JS: *onHeadersComplete /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:525:21
     26    0.1%    0.2%  JS: *wasm_on_body /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:149:21
     26    0.1%    0.2%  JS: *innerOk node:internal/assert/utils:259:17
     25    0.1%    0.2%  JS: *onDrain /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool-base.js:31:39

without headers

[JavaScript]:
   ticks  total  nonlib   name
    330    2.4%    2.4%  JS: *wasm-function[20]
    239    1.7%    1.7%  Builtin: KeyedLoadIC_Megamorphic
    188    1.4%    1.4%  JS: *parseHeaders /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/util.js:408:23
    136    1.0%    1.0%  Builtin: CreateTypedArray
    128    0.9%    0.9%  JS: *resumeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:958:19
    109    0.8%    0.8%  JS: *Request /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/core/request.js:31:15
    108    0.8%    0.8%  Builtin: RecordWriteSaveFP
    107    0.8%    0.8%  Builtin: LoadIC
     89    0.6%    0.6%  JS: *_resume /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:533:18
     85    0.6%    0.6%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool.js:75:20
     84    0.6%    0.6%  JS: *processTicksAndRejections node:internal/process/task_queues:72:35
     81    0.6%    0.6%  Builtin: KeyedStoreIC_Megamorphic
     80    0.6%    0.6%  JS: *Readable.read node:internal/streams/readable:647:35
     72    0.5%    0.5%  JS: *wasm_on_header_value /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:127:29
     70    0.5%    0.5%  JS: *nextTick node:internal/process/task_queues:113:18
     69    0.5%    0.5%  JS: *dump /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/api/readable.js:258:14
     59    0.4%    0.4%  Builtin: LoadIC_Megamorphic
     58    0.4%    0.4%  RegExp: [^\u0021-\u00ff]
     56    0.4%    0.4%  Builtin: RunMicrotasks
     53    0.4%    0.4%  JS: *<anonymous> /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client.js:279:15
     49    0.4%    0.4%  JS: *writeH1 /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:998:18
     46    0.3%    0.3%  JS: *runInAsyncScope node:async_hooks:204:18
     45    0.3%    0.3%  JS: *Readable node:internal/streams/readable:320:18
     44    0.3%    0.3%  Builtin: CallApiCallbackOptimizedNoProfiling
     37    0.3%    0.3%  JS: *wasm_on_header_field /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/client-h1.js:116:29
     37    0.3%    0.3%  Builtin: JSConstructStubGeneric
     37    0.3%    0.3%  Builtin: FulfillPromise
     35    0.3%    0.3%  JS: *request /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/api/api-request.js:176:18
     34    0.2%    0.2%  JS: *onDrain /node_modules/.pnpm/undici@7.2.0/node_modules/undici/lib/dispatcher/pool-base.js:31:39