From 3e9de33fa693a14e05143346646b2f87993cca4d Mon Sep 17 00:00:00 2001
From: William Deegan <bill@baddogconsulting.com>
Date: Sun, 4 Dec 2022 14:02:45 -0800
Subject: Added --experimental=tm_v2 which switches to use Andrew Morrow's new
 ParallelJob implementation. WHich should scale much better for highly
 parallel builds

---
 CHANGES.txt                    | 2 ++
 RELEASE.txt                    | 3 +++
 SCons/Script/SConsOptions.py   | 4 ++--
 SCons/Taskmaster/Job.py        | 7 ++++---
 doc/man/scons.xml              | 5 +++--
 test/option/taskmastertrace.py | 3 +--
 6 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 5e7f6d4..8818eed 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -32,6 +32,8 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Moved rpm and debian directories under packaging
     - Added logic to help packagers enable reproducible builds into packaging/etc/. Please
       read packaging/etc/README.txt if you are interested.
+    - Added --experimental=tm_v2, which enables Andrew Morrow's new NewParallel Job implementation.
+      This should scale much better for highly parallel builds.
 
   From Dan Mezhiborsky:
     - Add newline to end of compilation db (compile_commands.json).
diff --git a/RELEASE.txt b/RELEASE.txt
index 801062a..c7e7c4d 100644
--- a/RELEASE.txt
+++ b/RELEASE.txt
@@ -24,6 +24,9 @@ NEW FUNCTIONALITY
 - Added ValidateOptions() which will check that all command line options are in either
   those specified by SCons itself, or by AddOption() in SConstruct/SConscript.  It should
   not be called until all AddOption() calls are completed. Resolves Issue #4187
+- Added --experimental=tm_v2, which enables Andrew Morrow's NewParallel Job implementation.
+  This should scale much better for highly parallel builds.
+
 
 DEPRECATED FUNCTIONALITY
 ------------------------
diff --git a/SCons/Script/SConsOptions.py b/SCons/Script/SConsOptions.py
index f3b4708..a3e3ea8 100644
--- a/SCons/Script/SConsOptions.py
+++ b/SCons/Script/SConsOptions.py
@@ -40,7 +40,7 @@ SUPPRESS_HELP = optparse.SUPPRESS_HELP
 
 diskcheck_all = SCons.Node.FS.diskcheck_types()
 
-experimental_features = {'warp_speed', 'transporter', 'ninja'}
+experimental_features = {'warp_speed', 'transporter', 'ninja', 'tm_v2'}
 
 
 def diskcheck_convert(value):
@@ -65,7 +65,7 @@ def diskcheck_convert(value):
 class SConsValues(optparse.Values):
     """
     Holder class for uniform access to SCons options, regardless
-    of whether or not they can be set on the command line or in the
+    of whether they can be set on the command line or in the
     SConscript files (using the SetOption() function).
 
     A SCons option value can originate three different ways:
diff --git a/SCons/Taskmaster/Job.py b/SCons/Taskmaster/Job.py
index 853fe63..ef10df5 100644
--- a/SCons/Taskmaster/Job.py
+++ b/SCons/Taskmaster/Job.py
@@ -40,6 +40,7 @@ from enum import Enum
 import SCons.Errors
 import SCons.Warnings
 
+
 # The default stack size (in kilobytes) of the threads used to execute
 # jobs in parallel.
 #
@@ -53,8 +54,6 @@ default_stack_size = 256
 
 interrupt_msg = 'Build interrupted.'
 
-USE_NEW_PARALLEL = os.environ.get('SCONS_NEW_PARALLEL', False)
-
 class InterruptState:
     def __init__(self):
         self.interrupted = False
@@ -84,6 +83,7 @@ class Jobs:
         class can't do it, it gets reset to 1.  Wrapping interfaces that
         care should check the value of 'num_jobs' after initialization.
         """
+        from SCons.Script import GetOption
 
         self.job = None
         if num > 1:
@@ -92,10 +92,11 @@ class Jobs:
                 stack_size = default_stack_size
 
             try:
-                if USE_NEW_PARALLEL:
+                if 'tm_v2' in GetOption('experimental'):
                     self.job = NewParallel(taskmaster, num, stack_size)
                 else:
                     self.job = LegacyParallel(taskmaster, num, stack_size)
+
                 self.num_jobs = num
             except NameError:
                 pass
diff --git a/doc/man/scons.xml b/doc/man/scons.xml
index 0278d87..4f1987d 100644
--- a/doc/man/scons.xml
+++ b/doc/man/scons.xml
@@ -1125,11 +1125,12 @@ the mechanisms in the specified order.</para>
         the special tokens <literal>all</literal> or <literal>none</literal>.
         A comma-separated string can be used to select multiple features.
         The default setting is <literal>none</literal>.</para>
-      <para>Current available features are: <literal>ninja</literal>.</para>
+      <para>Current available features are: <literal>ninja</literal>, <literal>tm_v2</literal>.</para>
       <caution><para>
         No Support offered for any features or tools enabled by this flag.
       </para></caution>
-      <para><emphasis>Available since &scons; 4.2.</emphasis></para>
+        <para><emphasis><literal>ninja</literal>Available since &scons; 4.2.</emphasis></para>
+        <para><emphasis><literal>tm_v2</literal>Available since &scons; 4.4.1</emphasis></para>
     </listitem>
   </varlistentry>
 
diff --git a/test/option/taskmastertrace.py b/test/option/taskmastertrace.py
index 0e44896..f30d725 100644
--- a/test/option/taskmastertrace.py
+++ b/test/option/taskmastertrace.py
@@ -55,8 +55,7 @@ test.run(arguments='--taskmastertrace=trace.out .', stdout=expect_stdout)
 test.must_match_file('trace.out', 'taskmaster_expected_file_1.txt', mode='r')
 
 # Test NewParallel Job implementation
-os.environ['SCONS_NEW_PARALLEL'] = "1"
-test.run(arguments='-j 2 --taskmastertrace=new_parallel_trace.out .')
+test.run(arguments='-j 2 --experimental=tm_v2 --taskmastertrace=new_parallel_trace.out .')
 
 new_trace = test.read('new_parallel_trace.out', mode='r')
 thread_id = re.compile(r'\[Thread:\d+\]')
-- 
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