set default max_worker == 1, add '--max-install-thread' cmd arg

modules/cmd_args.py

@@ -31,6 +31,7 @@
 parser.add_argument("--no-half-vae", action='store_true', help="do not switch the VAE model to 16-bit floats")
 parser.add_argument("--no-progressbar-hiding", action='store_true', help="do not hide progressbar in gradio UI (we hide it because it slows down ML if you have hardware acceleration in browser)")
 parser.add_argument("--max-batch-count", type=int, default=16, help="does not do anything")
+parser.add_argument("--max-install-thread", type=int, default=1, help="Maximum Thread number for for asynchronously install extensions. 1 = normal install. ⚠ Enabling this feature may cause unintended issues with some extensions."),
 parser.add_argument("--embeddings-dir", type=normalized_filepath, default=os.path.join(data_path, 'embeddings'), help="embeddings directory for textual inversion (default: embeddings)")
 parser.add_argument("--textual-inversion-templates-dir", type=normalized_filepath, default=os.path.join(script_path, 'textual_inversion_templates'), help="directory with textual inversion templates")
 parser.add_argument("--hypernetwork-dir", type=normalized_filepath, default=os.path.join(models_path, 'hypernetworks'), help="hypernetwork directory")

modules/launch_utils.py

@@ -280,12 +280,19 @@ def run_extensions_installers(settings_file):
             if os.path.isdir(path):
                 paths[dirname_extension] = path
 
-        with ThreadPoolExecutor(max_workers=2) as executor:
-            futures = {executor.submit(run_extension_installer, path): dirname_extension for dirname_extension, path in paths.items()}
-            for future in as_completed(futures):
-                dirname_extension = futures[future]
-                if future.result():
-                    startup_timer.record(dirname_extension)
+        max_workers = args.max_install_thread
+        if max_workers == 1:
+            for dirname_extension, path in paths.items():
+                run_extension_installer(path)
+                startup_timer.record(dirname_extension)
+        else:
+            max_workers = min(max_workers, 4)
+            with ThreadPoolExecutor(max_workers=max_workers) as executor:
+                futures = {executor.submit(run_extension_installer, path): dirname_extension for dirname_extension, path in paths.items()}
+                for future in as_completed(futures):
+                    dirname_extension = futures[future]
+                    if future.result():
+                        startup_timer.record(dirname_extension)
 
 
 re_requirement = re.compile(r"\s*([-_a-zA-Z0-9]+)\s*(?:==\s*([-+_.a-zA-Z0-9]+))?\s*")