[Bugfix] Whisper fix number of allocated CrossAttn blocks per-request (#30772)

Signed-off-by: NickLucche <nlucches@redhat.com>
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Nicolò Lucchesi 2025-12-16 15:20:19 +01:00 committed by GitHub
parent 9dbbc59b15
commit 75eb302a2e
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@ -187,6 +187,12 @@ class Scheduler(SchedulerInterface):
if self.is_encoder_decoder
else EncoderCacheManager(cache_size=encoder_cache_size)
)
# For encoder-decoder models, allocate the maximum number of tokens for Cross
# Attn blocks, as for Whisper its input is always padded to the maximum length.
# TODO (NickLucche): Generalize to models with variable-length encoder inputs.
self._num_encoder_max_input_tokens = (
MULTIMODAL_REGISTRY.get_encdec_max_encoder_len(vllm_config.model_config)
)
speculative_config = vllm_config.speculative_config
self.use_eagle = False
@ -568,17 +574,11 @@ class Scheduler(SchedulerInterface):
0 if request.num_computed_tokens == 0 else self.num_lookahead_tokens
)
# Determine if we need to allocate cross-attention blocks.
if self.is_encoder_decoder and request.has_encoder_inputs:
# TODO(russellb): For Whisper, we know that the input is
# always padded to the maximum length. If we support other
# encoder-decoder models, this will need to be updated if we
# want to only allocate what is needed.
num_encoder_tokens = (
self.scheduler_config.max_num_encoder_input_tokens
)
else:
num_encoder_tokens = 0
num_encoder_tokens = (
self._num_encoder_max_input_tokens
if self.is_encoder_decoder and request.has_encoder_inputs
else 0
)
new_blocks = self.kv_cache_manager.allocate_slots(
request,