Avoid GPT-2 daily CI job OOM (in TF tests) (#24106)

* fix

* fix

---------

Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

tests/models/gpt2/test_modeling_gpt2.py

@@ -15,6 +15,7 @@
 
 
 import datetime
+import gc
 import math
 import unittest
 
@@ -500,6 +501,12 @@ def setUp(self):
         self.model_tester = GPT2ModelTester(self)
         self.config_tester = ConfigTester(self, config_class=GPT2Config, n_embd=37)
 
+    def tearDown(self):
+        super().tearDown()
+        # clean-up as much as possible GPU memory occupied by PyTorch
+        gc.collect()
+        torch.cuda.empty_cache()
+
     def test_config(self):
         self.config_tester.run_common_tests()
 
@@ -683,6 +690,12 @@ def test_model_from_pretrained(self):
 
 @require_torch
 class GPT2ModelLanguageGenerationTest(unittest.TestCase):
+    def tearDown(self):
+        super().tearDown()
+        # clean-up as much as possible GPU memory occupied by PyTorch
+        gc.collect()
+        torch.cuda.empty_cache()
+
     def _test_lm_generate_gpt2_helper(
         self,
         gradient_checkpointing=False,