[TPU][V1] Fix exponential padding when max-num-batched-tokens is not a power of 2 (vllm-project#16596)

Signed-off-by: NickLucche <nlucches@redhat.com>
Signed-off-by: Yang Wang <elainewy@meta.com>

Author: NickLucche

tests/v1/tpu/worker/test_tpu_model_runner.py

@@ -299,6 +299,18 @@ def test_get_paddings():
     actual_paddings = _get_token_paddings(min_token_size, max_token_size,
                                           padding_gap)
     assert actual_paddings == expected_paddings
+    # Exponential padding.
+    max_token_size, padding_gap = 1024, 0
+    expected_paddings = [16, 32, 64, 128, 256, 512, 1024]
+    actual_paddings = _get_token_paddings(min_token_size, max_token_size,
+                                          padding_gap)
+    assert actual_paddings == expected_paddings
+    # Exponential padding with max_token_size not a power of two.
+    max_token_size = 317
+    expected_paddings = [16, 32, 64, 128, 256, 512]
+    actual_paddings = _get_token_paddings(min_token_size, max_token_size,
+                                          padding_gap)
+    assert actual_paddings == expected_paddings
 
 
 def test_get_padded_token_len():

vllm/v1/worker/tpu_model_runner.py

@@ -1040,9 +1040,11 @@ def _get_token_paddings(min_token_size: int, max_token_size: int,
 
     if padding_gap == 0:
         logger.info("Using exponential token paddings:")
-        while num <= max_token_size:
+        while True:
             logger.info("    %d", num)
             paddings.append(num)
+            if num >= max_token_size:
+                break
             num *= 2
 
     else: