diff --git a/lib/paygen/paygen_build_lib.py b/lib/paygen/paygen_build_lib.py
index b2b537d..e89e33e 100644
--- a/lib/paygen/paygen_build_lib.py
+++ b/lib/paygen/paygen_build_lib.py
@@ -729,12 +729,16 @@
                       True)
                      for payload in payloads]
 
-    # delta_generator can eat gigs of RAM so we need to constrain the total
-    # number of such processes running at the same time. Also note that some
-    # other instances of this could be running at the same time so this
-    # number could have an additional multiplier applied to it.
+    # Most of the operations in paygen for one single payload is single threaded
+    # and mostly IO bound (downloading images, extracting partitions, waiting
+    # for signers, signing payload, etc). The only part that requires special
+    # attention is generating an unsigned payload which internally has a
+    # massively parallel implementation. So, here we allow multiple processes to
+    # run simultenously and we restrict the number of processes that do the
+    # unsigned payload generation to only two (look at _semaphore in
+    # paygen_payload_lib.py).
     parallel.RunTasksInProcessPool(paygen_payload_lib.CreateAndUploadPayload,
-                                   payloads_args, processes=2)
+                                   payloads_args, processes=8)
 
   def _FindFullTestPayloads(self, channel, version):
     """Returns a list of full test payloads for a given version.
diff --git a/lib/paygen/paygen_build_lib_unittest.py b/lib/paygen/paygen_build_lib_unittest.py
index bdf8ea0..d694d8e 100644
--- a/lib/paygen/paygen_build_lib_unittest.py
+++ b/lib/paygen/paygen_build_lib_unittest.py
@@ -826,7 +826,7 @@
                    [(self.mp_full_payload, True, True),
                     (self.mp_delta_payload, True, True),
                     (self.test_delta_payload, False, True)],
-                   processes=2)])
+                   processes=8)])
 
   def testCleanupBuild(self):
     """Test PaygenBuild._CleanupBuild."""
diff --git a/lib/paygen/paygen_payload_lib.py b/lib/paygen/paygen_payload_lib.py
index 1ec3af2..7b07786 100644
--- a/lib/paygen/paygen_payload_lib.py
+++ b/lib/paygen/paygen_payload_lib.py
@@ -10,10 +10,10 @@
 import base64
 import datetime
 import json
+import multiprocessing
 import os
 import shutil
 import tempfile
-import threading
 
 from chromite.lib import chroot_util
 from chromite.lib import constants
@@ -32,7 +32,8 @@
 DESCRIPTION_FILE_VERSION = 2
 
 # Only two parallel paygen for now.
-_semaphore = threading.Semaphore(2)
+_semaphore = multiprocessing.Semaphore(2)
+
 
 class Error(Exception):
   """Base class for payload generation errors."""
@@ -370,9 +371,8 @@
 
     # Do not run the delta_generator in parallel. It already has full
     # parallelism inside.
-    _semaphore.acquire()
-    self._RunGeneratorCmd(cmd)
-    _semaphore.release()
+    with _semaphore:
+      self._RunGeneratorCmd(cmd)
 
   def _GenerateHashes(self):
     """Generate a payload hash and a metadata hash.