Removed default limit of 4

Author: radarhere

docs/installation/building-from-source.rst

@@ -276,10 +276,9 @@ Build options
 
 * Config setting: ``-C parallel=n``. Can also be given
   with environment variable: ``MAX_CONCURRENCY=n``. Pillow can use
-  multiprocessing to build the extension. Setting ``-C parallel=n``
+  multiprocessing to build the extensions. Setting ``-C parallel=n``
   sets the number of CPUs to use to ``n``, or can disable parallel building by
-  using a setting of 1. By default, it uses 4 CPUs, or if 4 are not
-  available, as many as are present.
+  using a setting of 1. By default, it uses as many CPUs as are present.
 
 * Config settings: ``-C zlib=disable``, ``-C jpeg=disable``,
   ``-C tiff=disable``, ``-C freetype=disable``, ``-C raqm=disable``,

setup.py

@@ -28,7 +28,7 @@
     _, key, value = sys.argv.pop().split("=", 2)
     configuration.setdefault(key, []).append(value)
 
-default = int(configuration.get("parallel", ["4"])[-1])
+default = int(configuration.get("parallel", ["0"])[-1])
 ParallelCompile("MAX_CONCURRENCY", default).install()
 
 
@@ -394,9 +394,7 @@ def finalize_options(self) -> None:
             cpu_count = os.cpu_count()
             if cpu_count is not None:
                 try:
-                    self.parallel = int(
-                        os.environ.get("MAX_CONCURRENCY", min(4, cpu_count))
-                    )
+                    self.parallel = int(os.environ.get("MAX_CONCURRENCY", cpu_count))
                 except TypeError:
                     pass
         for x in self.feature: