perf: default network-concurrency to cpu count (#7285)

* feat: default network-concurrency to cpu count

It was found that setting network-concurrency to the exact number of
CPU cores gives fastest installation

* perf: set 16 as min default concurrency

* docs: add comment

---------

Co-authored-by: Zoltan Kochan <z@kochan.io>

.changeset/small-eels-cry.md

@@ -0,0 +1,6 @@
+---
+"@pnpm/resolve-dependencies": patch
+"pnpm": patch
+---
+
+(Important) Increased the default amount of allowed concurrent network request on systems that have more than 16 CPUs [#7285](https://github.com/pnpm/pnpm/pull/7285).

cspell.json

@@ -237,6 +237,7 @@
     "testcase",
     "todomvc",
     "tsparticles",
+    "underperformance",
     "undollar",
     "uninstallation",
     "unnest",

pkg-manager/package-requester/src/packageRequester.ts

@@ -1,4 +1,5 @@
 import { createReadStream, promises as fs } from 'fs'
+import os from 'os'
 import path from 'path'
 import {
   type FileType,
@@ -97,7 +98,10 @@ export function createPackageRequester (
   } {
   opts = opts || {}
 
-  const networkConcurrency = opts.networkConcurrency ?? 16
+  // A lower bound of 16 is enforced to prevent performance degradation,
+  // especially in CI environments. Tests with a threshold lower than 16
+  // have shown consistent underperformance.
+  const networkConcurrency = opts.networkConcurrency ?? Math.max(os.cpus().length, 16)
   const requestsQueue = new PQueue({
     concurrency: networkConcurrency,
   })