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Support TurboQuant for YOCO + sliding-window models (e.g., Gemma 4 E4B)#40108

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ctao456 wants to merge 35 commits intovllm-project:mainfrom
ctao456:feature/turboquant-yoco-sliding-window
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Support TurboQuant for YOCO + sliding-window models (e.g., Gemma 4 E4B)#40108
ctao456 wants to merge 35 commits intovllm-project:mainfrom
ctao456:feature/turboquant-yoco-sliding-window

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@ctao456 ctao456 commented Apr 17, 2026

This pull request introduces several improvements and bug fixes related to TurboQuant attention, sliding window support, and KV cache management. The main themes are: enhanced support for sliding window attention in TurboQuant, improved handling of YOCO (You Only Cache Once) architectures, and more robust/unified KV cache page size logic.

TurboQuant attention and sliding window support:

  • Added full support for sliding window attention in TurboQuant, including mask construction in PyTorch and efficient windowed decoding in the Triton kernel (turboquant_attn.py, triton_turboquant_decode.py). [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
  • Ensured that sliding window configuration is properly set on HuggingFace configs, bypassing strict dataclass validation when necessary (model.py).

YOCO (KV-sharing) architecture support:

  • Implemented apply_yoco_skip_alignment to ensure TurboQuant skip-layers are correctly aligned for YOCO architectures, preventing quantization error amplification and ensuring cache compatibility (turboquant/config.py, arg_utils.py). [1] [2]

KV cache management and unification:

  • Improved page size unification by using the least common multiple (LCM) instead of the maximum, ensuring compatibility when page sizes are not multiples, and added logic to avoid excessive block sizes by attempting to collapse to a uniform spec first (kv_cache_utils.py). [1] [2]
  • When adding KV-sharing layers to cache groups, ensured per-layer spec lookups are consistent by updating the uniform spec mapping (worker/utils.py).

Attention spec selection logic:

  • Refactored attention spec selection to ensure TurboQuant and sliding window logic are handled in the correct order (attention.py). [1] [2]

Other improvements:

  • Added gcd import for LCM calculation in page size unification (kv_cache_utils.py).

These changes collectively improve the robustness, correctness, and efficiency of TurboQuant and sliding window attention, especially for advanced architectures like YOCO and models with heterogeneous layer specs.

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@mergify mergify Bot added the v1 label Apr 17, 2026
@ctao456 ctao456 force-pushed the feature/turboquant-yoco-sliding-window branch from 1b99ca2 to 0ae20f8 Compare April 17, 2026 06:21
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Code Review

This pull request introduces support for YOCO-style KV-sharing and sliding windows within the TurboQuant (TQ) framework, primarily to support models like Gemma 4. Key changes include bypassing HuggingFace dataclass validation for sliding window settings, implementing logic to skip layers exceeding hardware limits or prone to error amplification in shared KV architectures, and ensuring consistent rotation matrices across sharing pairs. Additionally, the KV cache management was updated to use the Least Common Multiple (LCM) for page size unification, and Triton kernels were modified to support sliding window constraints. Feedback was provided regarding an inefficiency in the layer-skipping logic where a list was being sorted repeatedly inside a loop.

Comment thread vllm/engine/arg_utils.py Outdated
@ctao456 ctao456 changed the title Support TurboQuant for YOCO + sliding-window models (Gemma 4 E4B) Support TurboQuant for YOCO + sliding-window models (e.g., Gemma 4 E4B) Apr 17, 2026
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This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @ctao456.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

@mergify mergify Bot added the needs-rebase label Apr 20, 2026
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Hi @ctao456 do u have any performance metrics using vllm bench serve similar to #39931 (comment)

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ctao456 commented Apr 22, 2026

Hi @ctao456 do u have any performance metrics using vllm bench serve similar to #39931 (comment)

Got more results running more thorough 3-dim (kv cache capacity, accuracy, perf under serving scenarios) benchmark, device is 1x Intel Arc Pro B70, model google/gemma-4-E4B-it

==============================================================================
  1. KV-CACHE COMPRESSION
==============================================================================

  google/gemma-4-E4B-it
  Config                        KV tokens    vs baseline
  ----------------------    -------------  -------------
  turboquant_k8v4                 366,144          2.69x
  bf16                            136,256          1.00x
  turboquant_4bit_nc              407,808          2.99x
  turboquant_k3v4_nc              422,400          3.10x
  turboquant_3bit_nc              438,144          3.22x

==============================================================================
  2. QUALITY  (wikitext PPL / NIAH pass@total / GSM8K exact-match)
==============================================================================

  google/gemma-4-E4B-it
  Config                        PPL         NIAH      GSM8K
  ----------------------    -------  -----------  ---------
  turboquant_k8v4              -               -      0.660
  bf16                         -               -      0.690
  turboquant_4bit_nc           -               -      0.655
  turboquant_k3v4_nc           -               -      0.650
  turboquant_3bit_nc           -               -      0.635

==============================================================================
  3. PERFORMANCE
==============================================================================

  google/gemma-4-E4B-it

    Scenario: mixed
    Config                    Req/s   OutTok/s   TTFT(ms)   TPOT(ms)    ITL(ms)
    --------------------    -------  ---------  ---------  ---------  ---------
    turboquant_k8v4             0.6        326       3814       85.7       85.7
    bf16                        0.5        281       4058      100.7      100.7
    turboquant_4bit_nc          0.6        330       3560       84.8       84.8
    turboquant_k3v4_nc          0.6        328       3790       85.0       85.0
    turboquant_3bit_nc          0.6        324       3819       85.9       85.9

    Scenario: decode_heavy
    Config                    Req/s   OutTok/s   TTFT(ms)   TPOT(ms)    ITL(ms)
    --------------------    -------  ---------  ---------  ---------  ---------
    turboquant_k8v4             0.4        409        345       73.3       73.3
    bf16                        0.3        355        353       85.1       85.1
    turboquant_4bit_nc          0.4        410        337       72.7       72.7
    turboquant_k3v4_nc          0.4        407        337       73.3       73.3
    turboquant_3bit_nc          0.4        403        348       74.1       74.1

    Scenario: long_prefill
    Config                    Req/s   OutTok/s   TTFT(ms)   TPOT(ms)    ITL(ms)
    --------------------    -------  ---------  ---------  ---------  ---------
    turboquant_k8v4             0.2         22      39257     1118.3     1118.3
    bf16                        0.2         21      41827     1215.4     1215.4
    turboquant_4bit_nc          0.2         22      39049     1118.0     1118.0
    turboquant_k3v4_nc          0.2         22      38985     1117.7     1117.7
    turboquant_3bit_nc          0.2         22      38995     1118.5     1118.5

    Scenario: high_load
    Config                    Req/s   OutTok/s   TTFT(ms)   TPOT(ms)    ITL(ms)
    --------------------    -------  ---------  ---------  ---------  ---------
    turboquant_k8v4             2.5        314       5470      159.0      159.0
    bf16                        2.0        260       6222      194.6      194.6
    turboquant_4bit_nc          2.5        319       5470      155.7      155.7
    turboquant_k3v4_nc          2.5        317       5439      157.0      157.0
    turboquant_3bit_nc          2.5        314       5477      158.9      158.9

    Scenario: short_decode
    Config                    Req/s   OutTok/s   TTFT(ms)   TPOT(ms)    ITL(ms)
    --------------------    -------  ---------  ---------  ---------  ---------
    turboquant_k8v4             0.8        394       5466       66.0       66.0
    bf16                        0.7        350       5696       76.1       76.1
    turboquant_4bit_nc          0.9        451        824       64.6       64.6
    turboquant_k3v4_nc          0.9        452        800       64.6       64.6
    turboquant_3bit_nc          0.9        445        864       65.3       65.3

Serving scenarios detailed below

name	input_len	output_len	num_prompts	concurrency
short_decode	128	512	200	32
long_prefill	4096	128	200	32
mixed	512	512	200	32
high_load	512	128	500	64
decode_heavy	64	1024	200	32

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is it possible to add a test case?

Comment thread vllm/config/model.py Outdated
Comment thread vllm/engine/arg_utils.py Outdated
Comment on lines +1664 to +1666
# Also skip layers whose head dimension exceeds the XPU FMHA
# limit (256). Gemma 4 has global attention layers with
# global_head_dim=512 that cannot run through flash attention.
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will turboquant run on flash attention backend? I suppose it will run into triton based turboquant backend which should support 512 head dim.

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Yes thank you @xinyu-intel . I'm WIP in testing by installing vllm-xpu-kernels 0.1.6 that has head dim 512 support.

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After installing vllm-xpu-kernels 0.1.6 that has head dim 512 support and using latest transformers version that supports gemma4, all 3 test prompt outputs are correct (accuracy passed).

The skip list now has layers 5, 11, 17 (global attention, head_dim=512) included in TQ instead of skipped — and inference still works.

Completed: Test gemma4 TQ inference (2/2)

The latest vllm_xpu_kernels handles head_dim=512 natively. Results:

intel@b70-server-sc:~/ctao/vllm-fork/vllm$  docker exec vllm-test python3 -c "
> import os
> os.environ['VLLM_ATTENTION_BACKEND'] = 'TRITON_ATTN'
> from vllm import LLM, SamplingParams
> llm = LLM('google/gemma-4-E4B-it',
>     kv_cache_dtype='turboquant_k3v4_nc',
>     max_model_len=2048,
>     gpu_memory_utilization=0.95,
>     enforce_eager=True,
>     trust_remote_code=True)
> tok = llm.get_tokenizer()
> prompts_raw = [
>     'What is 2+2? Answer with just the number.',
>     'Explain gravity in 3 sentences.',
>     'Write a haiku about the moon.',
> ]
> prompts = []
> for p in prompts_raw:
>     prompts.append(tok.apply_chat_template([{'role':'user','content':p}], tokenize=False, add_generation_prompt=True))
> for o in llm.generate(prompts, SamplingParams(max_tokens=100)):
>     print('OUTPUT:', o.outputs[0].text[:200])
>     print()
> " 2>&1 | grep -E 'OUTPUT:|TQ:|skip|Error|Traceback|head_dim'
INFO 04-23 06:35:54 [arg_utils.py:1696] TQ: skipping KV-sharing target layers ['22', '23'] to prevent error amplification in YOCO architecture
INFO 04-23 06:35:54 [arg_utils.py:1720] TQ: after KV-sharing alignment, skip list: ['0', '1', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41']
INFO 04-23 06:35:54 [arg_utils.py:1726] TQ: skipping layers ['0', '1', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41'] for boundary protection (num_layers=42)
INFO 04-23 06:35:54 [config.py:101] Gemma4 model has heterogeneous head dimensions (head_dim=256, global_head_dim=512). Forcing TRITON_ATTN backend to prevent mixed-backend numerical divergence.
(EngineCore pid=14203) INFO 04-23 06:36:36 [core.py:107] Initializing a V1 LLM engine (v0.1.dev16022+g2905cc00e) with config: model='google/gemma-4-E4B-it', speculative_config=None, tokenizer='google/gemma-4-E4B-it', skip_tokenizer_init=False, tokenizer_mode=auto, revision=None, tokenizer_revision=None, trust_remote_code=True, dtype=torch.bfloat16, max_seq_len=2048, download_dir=None, load_format=auto, tensor_parallel_size=1, pipeline_parallel_size=1, data_parallel_size=1, decode_context_parallel_size=1, dcp_comm_backend=ag_rs, disable_custom_all_reduce=True, quantization=None, quantization_config=None, enforce_eager=True, enable_return_routed_experts=False, kv_cache_dtype=turboquant_k3v4_nc, device_config=xpu, structured_outputs_config=StructuredOutputsConfig(backend='auto', disable_any_whitespace=False, disable_additional_properties=False, reasoning_parser='', reasoning_parser_plugin='', enable_in_reasoning=False), observability_config=ObservabilityConfig(show_hidden_metrics_for_version=None, otlp_traces_endpoint=None, collect_detailed_traces=None, kv_cache_metrics=False, kv_cache_metrics_sample=0.01, cudagraph_metrics=False, enable_layerwise_nvtx_tracing=False, enable_mfu_metrics=False, enable_mm_processor_stats=False, enable_logging_iteration_details=False), seed=0, served_model_name=google/gemma-4-E4B-it, enable_prefix_caching=True, enable_chunked_prefill=True, pooler_config=None, compilation_config={'mode': <CompilationMode.NONE: 0>, 'debug_dump_path': None, 'cache_dir': '', 'compile_cache_save_format': 'binary', 'backend': 'inductor', 'custom_ops': ['all'], 'ir_enable_torch_wrap': False, 'splitting_ops': [], 'compile_mm_encoder': False, 'cudagraph_mm_encoder': False, 'encoder_cudagraph_token_budgets': [], 'encoder_cudagraph_max_vision_items_per_batch': 0, 'encoder_cudagraph_max_frames_per_batch': None, 'compile_sizes': [], 'compile_ranges_endpoints': [8192], 'inductor_compile_config': {'enable_auto_functionalized_v2': False, 'size_asserts': False, 'alignment_asserts': False, 'scalar_asserts': False, 'combo_kernels': True, 'benchmark_combo_kernel': True}, 'inductor_passes': {}, 'cudagraph_mode': <CUDAGraphMode.NONE: 0>, 'cudagraph_num_of_warmups': 0, 'cudagraph_capture_sizes': [], 'cudagraph_copy_inputs': False, 'cudagraph_specialize_lora': True, 'use_inductor_graph_partition': False, 'pass_config': {'fuse_norm_quant': True, 'fuse_act_quant': True, 'fuse_attn_quant': False, 'enable_sp': False, 'fuse_gemm_comms': False, 'fuse_allreduce_rms': False}, 'max_cudagraph_capture_size': 0, 'dynamic_shapes_config': {'type': <DynamicShapesType.BACKED: 'backed'>, 'evaluate_guards': False, 'assume_32_bit_indexing': False}, 'local_cache_dir': None, 'fast_moe_cold_start': True, 'static_all_moe_layers': []}, kernel_config=KernelConfig(ir_op_priority=IrOpPriorityConfig(rms_norm=['xpu_kernels', 'native']), enable_flashinfer_autotune=True, moe_backend='auto')
OUTPUT: 4
OUTPUT: Gravity is a fundamental force of nature that causes any two objects with mass to be attracted to each other. This attraction is what keeps planets in orbit around stars and keeps our feet on the grou
OUTPUT: Silver light hangs high,

Skip list before: [0, 1, 5, 11, 17, 22, 23, 24-41] (25 skipped, 17 TQ layers)
Skip list now: [0, 1, 22, 23, 24-41] (22 skipped, 20 TQ layers — layers 5, 11, 17 now use TQ)
Accuracy: All 3 prompts produce correct, coherent responses

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So that we can safely remove head dim > 256 layer skipping.

Comment thread vllm/v1/attention/backends/turboquant_attn.py
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@mgoin PTAL thanks

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ctao456 added 5 commits April 24, 2026 15:48
Signed-off-by: Tao, Chun <chun.tao@intel.com>
…hey're still incompatible, fall through to the LCM path which correctly raises NotImplementedError

Signed-off-by: Tao, Chun <chun.tao@intel.com>
Signed-off-by: Tao, Chun <chun.tao@intel.com>
…head_size=96 (mixed type) in test_kv_cache_utils

Signed-off-by: Tao, Chun <chun.tao@intel.com>
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Comment on lines +1657 to +1672
# When page sizes aren't clean multiples of each other, the LCM-based
# unification below creates excessively large blocks. Try converting
# SlidingWindowSpec / ChunkedLocalAttentionSpec → FullAttentionSpec
# first: if that collapses all specs into one uniform type, the
# single-group path avoids the LCM blow-up entirely.
page_sizes = {s.page_size_bytes for s in kv_cache_spec.values()}
if len(page_sizes) > 1 and max(page_sizes) % min(page_sizes) != 0:
try:
unify_hybrid_kv_cache_specs(kv_cache_spec)
except ValueError:
pass # Could not fully unify; fall through to LCM path
else:
if is_kv_cache_spec_uniform(kv_cache_spec):
return _get_kv_cache_groups_uniform_spec(kv_cache_spec)
elif uniform_spec := UniformTypeKVCacheSpecs.from_specs(kv_cache_spec):
return _get_kv_cache_groups_uniform_type(uniform_spec)
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I find this logic confusing; i think it would be simpler if we just recommended users to do --disable-hybrid-kv-cache-manager for TQ + Gemma4; im not convinced for all sliding window + full attention + TQ models we want this behavior

cc @heheda12345 thoughts?

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Signed-off-by: Tao, Chun <chun.tao@intel.com>
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