fix(warmup): make warmup work for smallest prefill size

Also, add timing checks in warmup test.

text-generation-inference/server/text_generation_server/jetstream_pt_support/generator.py

@@ -340,8 +340,8 @@ def warmup(self, batch: Batch) -> int:
             # Skip all the unsupported lengths
             if l > bucket_seq_len:
                 continue
-            # create a dummy request with the current sequence length
-            dummy_request = self._create_dummy_request(l)
+            # create a dummy request with the current sequence length -1 (so it gets padded up to l)
+            dummy_request = self._create_dummy_request(l - 1)
             # We define few max_new_tokens to request at least one (by prefill) and another by decode.
             MAX_NEW_TOKENS = 10
             dummy_request.stopping_parameters.max_new_tokens = MAX_NEW_TOKENS

text-generation-inference/tests/test_warmup.py

@@ -1,5 +1,7 @@
 
 
+from time import time
+
 import pytest
 from helpers import create_request, prepare_model
 from text_generation_server.auto_generator import AutoGenerator
@@ -14,17 +16,32 @@ def test_warmup_jetstream_pytorch():
     model_id = "Maykeye/TinyLLama-v0"
 
     # The maximum sequence length of the model is set to 1000, but warmup will round that up to the next power of two
-    # in prefill (1024).
-    sequence_length = 1000
+    # in prefill (256).
+    sequence_length = 250
 
     model_path = prepare_model(model_id, sequence_length)
     input_text = "It was a bright cold day in April, and the clocks were striking thirteen."
     max_new_tokens = 20
 
     generator = AutoGenerator.from_pretrained(
-        model_path, revision="", max_batch_size=1, max_sequence_length=sequence_length
+        model_path, revision="", max_batch_size=2, max_sequence_length=sequence_length
     )
     request = create_request(id=0, inputs=input_text, max_new_tokens=max_new_tokens, do_sample=False)
     batch = Batch(id=0, requests=[request], size=1, max_tokens=sequence_length)
     generator.warmup(batch)
 
+    # Prepare a new request with different settings. Warmup should have triggered compilation so this can be run
+    # quickly.
+    input_text = "What is Deep Learning?"
+    max_new_tokens = 3
+    max_tokens = 13
+    request1 = create_request(id=0, inputs=input_text, max_new_tokens=max_new_tokens, do_sample=False)
+    batch = Batch(id=1, requests=[request1], size=1, max_tokens=max_tokens)
+
+    start = time()
+    _generations, new_batch =  generator.prefill(batch)
+    _generations, new_batch =  generator.decode([new_batch])
+    end = time()
+
+    # Prefill and decode time should be less than 1 second (rather fast)
+    assert end - start < 1.0