diff --git a/lib/parallel.rb b/lib/parallel.rb
index c7f2bf6..b22ef29 100644
--- a/lib/parallel.rb
+++ b/lib/parallel.rb
@@ -1,11 +1,8 @@
 # frozen_string_literal: true
 require 'rbconfig'
 require 'parallel/version'
-require 'parallel/processor_count'
 
 module Parallel
-  extend ProcessorCount
-
   Stop = Object.new.freeze
 
   class DeadWorker < StandardError
@@ -307,6 +304,45 @@ def flat_map(*args, &block)
       map(*args, &block).flatten(1)
     end
 
+    # Number of physical processor cores on the current system.
+    def physical_processor_count
+      @physical_processor_count ||= begin
+        ppc =
+          case RbConfig::CONFIG["target_os"]
+          when /darwin[12]/
+            IO.popen("/usr/sbin/sysctl -n hw.physicalcpu").read.to_i
+          when /linux/
+            cores = {} # unique physical ID / core ID combinations
+            phy = 0
+            File.read("/proc/cpuinfo").scan(/^physical id.*|^core id.*/) do |ln|
+              if ln.start_with?("physical")
+                phy = ln[/\d+/]
+              elsif ln.start_with?("core")
+                cid = "#{phy}:#{ln[/\d+/]}"
+                cores[cid] = true unless cores[cid]
+              end
+            end
+            cores.count
+          when /mswin|mingw/
+            require 'win32ole'
+            result_set = WIN32OLE.connect("winmgmts://").ExecQuery(
+              "select NumberOfCores from Win32_Processor"
+            )
+            result_set.to_enum.collect(&:NumberOfCores).reduce(:+)
+          else
+            processor_count
+          end
+        # fall back to logical count if physical info is invalid
+        ppc > 0 ? ppc : processor_count
+      end
+    end
+
+    # Number of processors seen by the OS, used for process scheduling
+    def processor_count
+      require 'etc'
+      @processor_count ||= Integer(ENV['PARALLEL_PROCESSOR_COUNT'] || Etc.nprocessors)
+    end
+
     def worker_number
       Thread.current[:parallel_worker_number]
     end
diff --git a/lib/parallel/processor_count.rb b/lib/parallel/processor_count.rb
deleted file mode 100644
index 3b5ea61..0000000
--- a/lib/parallel/processor_count.rb
+++ /dev/null
@@ -1,44 +0,0 @@
-# frozen_string_literal: true
-module Parallel
-  # TODO: inline this method into parallel.rb and kill physical_processor_count in next major release
-  module ProcessorCount
-    # Number of processors seen by the OS, used for process scheduling
-    def processor_count
-      require 'etc'
-      @processor_count ||= Integer(ENV['PARALLEL_PROCESSOR_COUNT'] || Etc.nprocessors)
-    end
-
-    # Number of physical processor cores on the current system.
-    def physical_processor_count
-      @physical_processor_count ||= begin
-        ppc =
-          case RbConfig::CONFIG["target_os"]
-          when /darwin[12]/
-            IO.popen("/usr/sbin/sysctl -n hw.physicalcpu").read.to_i
-          when /linux/
-            cores = {} # unique physical ID / core ID combinations
-            phy = 0
-            File.read("/proc/cpuinfo").scan(/^physical id.*|^core id.*/) do |ln|
-              if ln.start_with?("physical")
-                phy = ln[/\d+/]
-              elsif ln.start_with?("core")
-                cid = "#{phy}:#{ln[/\d+/]}"
-                cores[cid] = true unless cores[cid]
-              end
-            end
-            cores.count
-          when /mswin|mingw/
-            require 'win32ole'
-            result_set = WIN32OLE.connect("winmgmts://").ExecQuery(
-              "select NumberOfCores from Win32_Processor"
-            )
-            result_set.to_enum.collect(&:NumberOfCores).reduce(:+)
-          else
-            processor_count
-          end
-        # fall back to logical count if physical info is invalid
-        ppc > 0 ? ppc : processor_count
-      end
-    end
-  end
-end