diff --git a/doc/ext/extra_specs.py b/doc/ext/extra_specs.py
index 2963ee275685..7e1133533d5f 100644
--- a/doc/ext/extra_specs.py
+++ b/doc/ext/extra_specs.py
@@ -224,7 +224,16 @@ class NovaDomain(domains.Domain):
             )
         return None
 
+    def merge_domaindata(self, docnames, otherdata):
+        for target, docname in otherdata['extra_specs'].items():
+            if docname in docnames:
+                self.data['extra_specs'][target] = docname
+
 
 def setup(app):
     app.add_domain(NovaDomain)
     app.add_directive('extra-specs', ExtraSpecGroupDirective)
+    return {
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/doc/ext/feature_matrix.py b/doc/ext/feature_matrix.py
index f0e9f92292e1..caeaecfad8c1 100644
--- a/doc/ext/feature_matrix.py
+++ b/doc/ext/feature_matrix.py
@@ -576,3 +576,7 @@ class FeatureMatrixDirective(rst.Directive):
 def setup(app):
     app.add_directive('feature_matrix', FeatureMatrixDirective)
     app.add_stylesheet('feature-matrix.css')
+    return {
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/doc/ext/versioned_notifications.py b/doc/ext/versioned_notifications.py
index 09a7621c8a24..244e0783b8ef 100644
--- a/doc/ext/versioned_notifications.py
+++ b/doc/ext/versioned_notifications.py
@@ -161,5 +161,9 @@ jQuery(document).ready(function(){
 
 
 def setup(app):
-    app.add_directive('versioned_notifications',
-                      VersionedNotificationDirective)
+    app.add_directive(
+        'versioned_notifications', VersionedNotificationDirective)
+    return {
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }
diff --git a/doc/requirements.txt b/doc/requirements.txt
index 946d4519da2f..df112fe733f0 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -5,7 +5,7 @@ sphinx>=2.0.0,!=2.1.0 # BSD
 sphinxcontrib-actdiag>=0.8.5 # BSD
 sphinxcontrib-seqdiag>=0.8.4 # BSD
 sphinxcontrib-svg2pdfconverter>=0.1.0 # BSD
-sphinx-feature-classification>=0.2.0 # Apache-2.0
+sphinx-feature-classification>=1.1.0 # Apache-2.0
 os-api-ref>=1.4.0 # Apache-2.0
 openstackdocstheme>=2.2.0 # Apache-2.0
 
diff --git a/tox.ini b/tox.ini
index e46a82ced9fb..8b2542e42c28 100644
--- a/tox.ini
+++ b/tox.ini
@@ -185,7 +185,7 @@ deps =
   -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf doc/build/html doc/build/doctrees
-  sphinx-build -W --keep-going -b html -d doc/build/doctrees doc/source doc/build/html
+  sphinx-build -W --keep-going -b html -j auto doc/source doc/build/html
   # Test the redirects. This must run after the main docs build
   whereto doc/build/html/.htaccess doc/test/redirect-tests.txt
 
@@ -196,7 +196,7 @@ envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 commands =
   rm -rf doc/build/pdf
-  sphinx-build -W -b latex doc/source doc/build/pdf
+  sphinx-build -W --keep-going -b latex -j auto doc/source doc/build/pdf
   make -C doc/build/pdf
 
 [testenv:api-guide]
@@ -206,7 +206,7 @@ envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 commands =
   rm -rf api-guide/build
-  sphinx-build -W --keep-going -b html -d api-guide/build/doctrees api-guide/source api-guide/build/html
+  sphinx-build -W --keep-going -b html -j auto api-guide/source api-guide/build/html
 
 [testenv:api-ref]
 description =
@@ -215,7 +215,7 @@ envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 commands =
   rm -rf api-ref/build
-  sphinx-build -W --keep-going -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html
+  sphinx-build -W --keep-going -b html -j auto api-ref/source api-ref/build/html
 
 [testenv:releasenotes]
 description =
@@ -224,7 +224,7 @@ envdir = {toxworkdir}/docs
 deps = {[testenv:docs]deps}
 commands =
   rm -rf releasenotes/build
-  sphinx-build -W --keep-going -b html -d releasenotes/build/doctrees releasenotes/source releasenotes/build/html
+  sphinx-build -W --keep-going -b html -j auto releasenotes/source releasenotes/build/html
 
 [testenv:all-docs]
 description =