Make max_num_batched_tokens behavior more verbose, add legacy mode (H…

…abanaAI#208)

Addressing issues from HabanaAI#207
Now, filtering behavior is more verbose, handling common errors and
displaying numbers of omitted buckets due to token budget (in debug log
level, buckets are printed):

```
INFO 08-27 20:57:27 profiler.py:62] Profiler enabled for: vllm-instance-1ab4f6c4d726480d8825044cf74e9af1
WARNING 08-27 20:57:27 utils.py:566] Pin memory is not supported on HPU.
INFO 08-27 20:57:27 selector.py:85] Using HabanaAttention backend.
INFO 08-27 20:57:27 habana_model_runner.py:563] Prompt bucket config (min, step, max_warmup) bs:[1, 32, 64], seq:[128, 128, 1024]
INFO 08-27 20:57:27 habana_model_runner.py:576] Generated 23 prompt buckets: [(1, 128), (1, 256), (1, 384), (1, 512), (1, 640), (1, 768), (1, 896), (1, 1024), (2, 128), (2, 256), (2, 384), (2, 512), (2, 640), (2, 768), (2, 896), (2, 1024), (4, 128), (4, 256), (4, 384), (4, 512), (8, 128), (8, 256), (16, 128)]
INFO 08-27 20:57:27 habana_model_runner.py:581] Omitted 33 prompt buckets due to exceeded token budget (max_num_batched_tokens=2048)
INFO 08-27 20:57:27 habana_model_runner.py:589] Decode bucket config (min, step, max_warmup) bs:[1, 128, 256], seq:[128, 128, 2048]
INFO 08-27 20:57:27 habana_model_runner.py:600] Generated 31 decode buckets: [(1, 128), (1, 256), (1, 384), (1, 512), (1, 640), (1, 768), (1, 896), (1, 1024), (1, 1152), (1, 1280), (1, 1408), (1, 1536), (1, 1664), (1, 1792), (1, 1920), (1, 2048), (2, 128), (2, 256), (2, 384), (2, 512), (2, 640), (2, 768), (2, 896), (2, 1024), (4, 128), (4, 256), (4, 384), (4, 512), (8, 128), (8, 256), (16, 128)]
INFO 08-27 20:57:27 habana_model_runner.py:605] Omitted 113 decode buckets due to exceeded token budget (max_num_batched_tokens=2048)
```

Legacy mode was also added, which throws a nasty error message whenever
token budget is set too low, but then it omits filtering and works as it
did previously (ran with ``VLLM_DECODE_BS_BUCKET_MIN=128
VLLM_DECODE_SEQ_BUCKET_MIN=1024 python vllm_test.py
--max-num-batched-tokens=2048``):

```
INFO 08-27 21:01:02 profiler.py:62] Profiler enabled for: vllm-instance-51f60d3978d347e992436f1dc0aa4702
WARNING 08-27 21:01:02 utils.py:566] Pin memory is not supported on HPU.
INFO 08-27 21:01:02 selector.py:85] Using HabanaAttention backend.
INFO 08-27 21:01:02 habana_model_runner.py:563] Prompt bucket config (min, step, max_warmup) bs:[1, 32, 64], seq:[128, 128, 1024]
INFO 08-27 21:01:02 habana_model_runner.py:576] Generated 23 prompt buckets: [(1, 128), (1, 256), (1, 384), (1, 512), (1, 640), (1, 768), (1, 896), (1, 1024), (2, 128), (2, 256), (2, 384), (2, 512), (2, 640), (2, 768), (2, 896), (2, 1024), (4, 128), (4, 256), (4, 384), (4, 512), (8, 128), (8, 256), (16, 128)]
INFO 08-27 21:01:02 habana_model_runner.py:581] Omitted 33 prompt buckets due to exceeded token budget (max_num_batched_tokens=2048)
INFO 08-27 21:01:02 habana_model_runner.py:589] Decode bucket config (min, step, max_warmup) bs:[128, 128, 256], seq:[1024, 128, 2048]
ERROR 08-27 21:01:02 habana_model_runner.py:128] The current bucketing configuration (min, step, max_warmup): bs:[128, 128, 256], seq:[1024, 128, 2048] cannot be used with specified max_num_batched_tokens (2048), as the smallest bucket (16384) would exceed token budget. Please increase max_num_batched_tokens or decrease bucket minimum Ignoring max_num_batched_tokens at risk of out-of-memory errors.
INFO 08-27 21:01:02 habana_model_runner.py:600] Generated 32 decode buckets: [(128, 128), (128, 256), (128, 384), (128, 512), (128, 640), (128, 768), (128, 896), (128, 1024), (128, 1152), (128, 1280), (128, 1408), (128, 1536), (128, 1664), (128, 1792), (128, 1920), (128, 2048), (256, 128), (256, 256), (256, 384), (256, 512), (256, 640), (256, 768), (256, 896), (256, 1024), (256, 1152), (256, 1280), (256, 1408), (256, 1536), (256, 1664), (256, 1792), (256, 1920), (256, 2048)]
INFO 08-27 21:01:02 habana_model_runner.py:605] Omitted 0 decode buckets due to exceeded token budget (max_num_batched_tokens=2048)
```

vllm/worker/habana_model_runner.py

@@ -96,14 +96,44 @@ def warmup_range(config: Tuple[int, int, int]):
 
 def warmup_buckets(bs_bucket_config, seq_bucket_config,
                    max_num_batched_tokens):
-    buckets = itertools.product(warmup_range(bs_bucket_config),
-                                warmup_range(seq_bucket_config))
+    buckets = list(
+        itertools.product(warmup_range(bs_bucket_config),
+                          warmup_range(seq_bucket_config)))
+    if len(buckets) == 0:
+        msg = ("No buckets could be captured with following config "
+               f"(min, step, max_warmup): "
+               f"bs:{bs_bucket_config}, "
+               f"seq:{seq_bucket_config}")
+        raise ValueError(msg)
+
     # Remove buckets exceeding batch token budget
-    filtered_buckets = filter(
-        lambda bucket: bucket[0] * bucket[1] <= max_num_batched_tokens,
-        buckets)
-    return list(
+    filtered_buckets = list(
+        filter(lambda bucket: bucket[0] * bucket[1] <= max_num_batched_tokens,
+               buckets))
+
+    if len(filtered_buckets) == 0:
+        # legacy case - we can handle this if we ignore max_num_batched_tokens
+        min_bucket_bs, min_bucket_seq = min(buckets,
+                                            key=lambda b: (b[0] * b[1]))
+        min_reqd_budget = min_bucket_bs * min_bucket_seq
+        msg = (
+            "The current bucketing configuration "
+            f"(min, step, max_warmup): "
+            f"bs:{bs_bucket_config}, "
+            f"seq:{seq_bucket_config} cannot be used with specified "
+            f"max_num_batched_tokens ({max_num_batched_tokens}), as the "
+            f"smallest bucket ({min_reqd_budget}) would exceed token budget. "
+            "Please increase max_num_batched_tokens or decrease bucket minimum "
+            "Ignoring max_num_batched_tokens at risk of out-of-memory errors.")
+        logger.error(msg)
+        return list(sorted(buckets, key=lambda b:
+                           (b[0] * b[1], b[1], b[0]))), []
+
+    captured_buckets = list(
         sorted(filtered_buckets, key=lambda b: (b[0] * b[1], b[1], b[0])))
+    omitted_buckets = list(
+        sorted([x for x in buckets if x not in filtered_buckets]))
+    return captured_buckets, omitted_buckets
 
 
 def next_pow2(value: int):
@@ -531,9 +561,9 @@ def _setup_buckets(self) -> None:
                f"bs:{self.prompt_bs_bucket_cfg}, "
                f"seq:{self.prompt_seq_bucket_cfg}")
         logger.info(msg)
-        self.prompt_buckets = warmup_buckets(self.prompt_bs_bucket_cfg,
-                                             self.prompt_seq_bucket_cfg,
-                                             self.max_num_batched_tokens)
+        self.prompt_buckets, prompt_omitted_buckets = warmup_buckets(
+            self.prompt_bs_bucket_cfg, self.prompt_seq_bucket_cfg,
+            self.max_num_batched_tokens)
 
         if self.lora_config:
             self.prompt_buckets[:] = [
@@ -545,13 +575,21 @@ def _setup_buckets(self) -> None:
                f"prompt buckets: {list(sorted(self.prompt_buckets))}")
         logger.info(msg)
 
+        msg = (f"Omitted {len(prompt_omitted_buckets)} "
+               "prompt buckets due to exceeded token budget "
+               f"(max_num_batched_tokens={self.max_num_batched_tokens})")
+        logger.info(msg)
+
+        msg = f"Omitted prompt buckets: {list(sorted(prompt_omitted_buckets))}"
+        logger.debug(msg)
+
         msg = ("Decode bucket config (min, step, max_warmup) "
                f"bs:{self.decode_bs_bucket_cfg}, "
                f"seq:{self.decode_seq_bucket_cfg}")
         logger.info(msg)
-        self.decode_buckets = warmup_buckets(self.decode_bs_bucket_cfg,
-                                             self.decode_seq_bucket_cfg,
-                                             self.max_num_batched_tokens)
+        self.decode_buckets, decode_omitted_buckets = warmup_buckets(
+            self.decode_bs_bucket_cfg, self.decode_seq_bucket_cfg,
+            self.max_num_batched_tokens)
         if self.lora_config:
             self.decode_buckets[:] = [
                 bucket for bucket in self.decode_buckets
@@ -561,6 +599,14 @@ def _setup_buckets(self) -> None:
                f"{list(sorted(self.decode_buckets))}")
         logger.info(msg)
 
+        msg = (f"Omitted {len(decode_omitted_buckets)} "
+               "decode buckets due to exceeded token budget "
+               f"(max_num_batched_tokens={self.max_num_batched_tokens})")
+        logger.info(msg)
+
+        msg = f"Omitted decode buckets: {list(sorted(decode_omitted_buckets))}"
+        logger.debug(msg)
+
     def _prepare_prompt(
         self,
         seq_group_metadata_list: List[SequenceGroupMetadata],