[Docs] optimize and supplement docs system (#86)

Signed-off-by: Gaohan123 <gaohan19@huawei.com>

docs/configuration/README.md

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+# Configuration Options
+
+This section lists the most common options for running vLLM-Omni.
+
+For options within a vLLM Engine. Please refer to [vLLM Configuration](https://docs.vllm.ai/en/v0.11.0/configuration/index.html)
+
+Currently, the main options are maintained by stage configs for each model.
+
+For specific example, please refer to [Qwen2.5-omni stage config](stage_configs/qwen2_5_omni.yaml)
+
+For introduction, please check [Introduction for stage config](./stage_configs.md)

docs/configuration/stage_configs.md

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+# Stage configs for vLLM-Omni
+
+In vLLM-Omni, it divides models in vLLM-omni into multiple stages, which are processed by different LLMEngines, DiffusionEngines or other kinds of engines. According to different types of stages, such as AR stage or DiT stage, each stage can choose corresponding schedulers, model workers to load into Engines with a plug-in way.
+
+Therefore, the stage configs for a model have several main functions:
+
+- Claim partition of stages and corresponding class implementation in the folder model_executor/models.
+- The disaggregated configuration for each stage and the communication topology among them.
+- Engine arguments for each engine within the stage.
+- Input and output dependencies for each stage.
+- Default input parameters.
+
+If users want to modify some part of it. The custom stage_configs file can be input as input argument in both online and offline. Just like examples below:
+
+For offline (Assume necessary dependencies have ben imported):
+```python
+model_name = "Qwen/Qwen2.5-Omni-7B"
+omni_llm = OmniLLM(model=model_name, stage_configs_path="/path/to/custom_stage_configs.yaml")
+```
+
+For online serving:
+```bash
+vllm serve Qwen/Qwen2.5-Omni-7B --omni --port 8091 --stage-configs-path /path/to/stage_configs_file
+```
+
+Below is a specific example of stage_configs.yaml in Qwen2.5-omni.
+```python
+# stage config for running qwen2.5-omni with architecture of OmniLLM.
+stage_args:
+  - stage_id: 0 # mark the unique id for each stage
+    runtime: # The disaggregated configuration
+      process: true  # Run this stage in a separate process
+      devices: "0" # Visible devices for this stage (CUDA_VISIBLE_DEVICES/torch.cuda.set_device)
+      max_batch_size: 1 # the batch_size for offline inference
+    engine_args: # Engine arguments for a certain engine
+      model_stage: thinker
+      model_arch: Qwen2_5OmniForConditionalGeneration # The model implementation registered in model_executor/models/registry.py
+      worker_cls: vllm_omni.worker.gpu_ar_worker.GPUARWorker # The specific worker used
+      scheduler_cls: vllm_omni.core.sched.scheduler.OmniScheduler # The specific scehduler used
+      gpu_memory_utilization: 0.8 # The gpu memory allocation for the stage within a single chip
+      enforce_eager: true  # Now we only support eager mode
+      trust_remote_code: true # Needed by huggingface config parsing
+      engine_output_type: latent  # It claims that the stage will input latent hiddenstates besides token ids
+      enable_prefix_caching: false # For request with hiddenstates output, the prefix caching is not supported now
+    is_comprehension: true # If the stage is a text or multimodal comprehension module. If it is, the AsyncOmniLLM will use its tokenizer as default
+    final_output: true # If the stage has output as part of final outputs. If it is false, which means that the stage only works as a intermediate role.
+    final_output_type: text # What is the final output type. It can be text and audio now.
+    default_sampling_params: # sampling parameters for the stage. Their meaning aligns with vLLM.
+      temperature: 0.0
+      top_p: 1.0
+      top_k: -1
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.1
+  - stage_id: 1
+    runtime:
+      process: true
+      devices: "1"
+      max_batch_size: 3
+    engine_args:
+      model_stage: talker
+      model_arch: Qwen2_5OmniForConditionalGeneration
+      worker_cls: vllm_omni.worker.gpu_ar_worker.GPUARWorker
+      scheduler_cls: vllm_omni.core.sched.scheduler.OmniScheduler
+      gpu_memory_utilization: 0.8
+      enforce_eager: true
+      trust_remote_code: true
+      enable_prefix_caching: false
+      engine_output_type: latent
+    engine_input_source: [0]
+    custom_process_input_func: vllm_omni.model_executor.stage_input_processors.qwen2_5_omni.thinker2talker
+    default_sampling_params:
+      temperature: 0.9
+      top_p: 0.8
+      top_k: 40
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.05
+      stop_token_ids: [8294]
+  - stage_id: 2
+    runtime:
+      process: true
+      devices: "0"            # Example: use a different GPU than the previous stage; use "0" if single GPU
+      max_batch_size: 1
+    engine_args:
+      model_stage: code2wav
+      model_arch: Qwen2_5OmniForConditionalGeneration
+      worker_cls: vllm_omni.worker.gpu_diffusion_worker.GPUDiffusionWorker
+      scheduler_cls: vllm_omni.core.sched.diffusion_scheduler.DiffusionScheduler
+      gpu_memory_utilization: 0.15
+      enforce_eager: true
+      trust_remote_code: true
+      enable_prefix_caching: false
+      engine_output_type: audio
+    engine_input_source: [1]
+    final_output: true
+    final_output_type: audio
+    default_sampling_params:
+      temperature: 0.0
+      top_p: 1.0
+      top_k: -1
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.1
+
+# Top-level runtime config (concise): default windows and stage edges
+runtime:
+  enabled: true
+  defaults:
+    window_size: -1             # Simplified: trigger downstream only after full upstream completion
+    max_inflight: 1             # Simplified: process serially within each stage
+  edges:
+    - from: 0                   # thinker → talker: trigger only after receiving full input (-1)
+      to: 1
+      window_size: -1
+    - from: 1                   # talker → code2wav: trigger only after receiving full input (-1)
+      to: 2
+      window_size: -1
+
+```
+
+## Stage Configuration Arguments
+
+Each stage in the `stage_args` list contains the following configuration options:
+
+### `stage_id`
+
+A unique identifier for each stage in the multi-stage pipeline. Stages are numbered sequentially starting from 0, and this ID is used to reference stages in inter-stage dependencies (e.g., `engine_input_source`).
+
+### `runtime`
+
+Configuration for disaggregated execution of the stage, controlling how the stage is deployed and executed.
+
+#### `runtime.process`
+
+Whether to run this stage in a separate process. When set to `true`, the stage will be executed in an isolated process, enabling better resource isolation and parallel execution across different stages. This is essential for multi-GPU deployments where different stages run on different devices.
+
+Default: `true`
+
+#### `runtime.devices`
+
+Visible devices for this stage, specified as a string. This controls which GPU devices are available to the stage process, similar to setting `CUDA_VISIBLE_DEVICES` or using `torch.cuda.set_device()`. For example, `"0"` uses GPU 0, `"1"` uses GPU 1, and `"0,1"` makes both GPUs 0 and 1 visible.
+
+Default: `"0"`
+
+#### `runtime.max_batch_size`
+
+The maximum batch size for offline inference in this stage. This limits how many sequences can be processed together in a single batch during offline inference operations.
+
+Default: `1`
+
+### `engine_args`
+
+Engine arguments for configuring the LLM engine, diffusion engine, or other engine types used by this stage.
+
+#### `engine_args.model_stage`
+
+The name identifier for this model stage within the multi-stage architecture. This is used internally to distinguish different stages of the same model (e.g., "thinker", "talker", "code2wav" in Qwen2.5-Omni).
+
+#### `engine_args.model_arch`
+
+The model architecture class name that is registered in `model_executor/models/registry.py`. This specifies which model implementation to use for this stage. The class must be registered in the model registry for vLLM-Omni to locate and instantiate it.
+
+#### `engine_args.worker_cls`
+
+The specific worker class to use for this stage. This determines how the model computations are executed. Examples include `vllm_omni.worker.gpu_ar_worker.GPUARWorker` for autoregressive stages and `vllm_omni.worker.gpu_diffusion_worker.GPUDiffusionWorker` for diffusion-based stages.
+
+#### `engine_args.scheduler_cls`
+
+The scheduler class to use for this stage. The scheduler manages request queuing, batching, and execution order. Examples include `vllm_omni.core.sched.scheduler.OmniScheduler` for standard stages and `vllm_omni.core.sched.diffusion_scheduler.DiffusionScheduler` for diffusion stages.
+
+#### `engine_args.gpu_memory_utilization`
+
+The fraction of GPU memory to allocate for this stage within a single GPU chip. This is a value between 0.0 and 1.0, where 0.8 means 80% of the GPU memory will be used by this stage. This allows fine-grained control over memory allocation when multiple stages share the same GPU or when reserving memory for other operations.
+
+Default: `0.8`
+
+#### `engine_args.enforce_eager`
+
+Whether to enforce eager execution mode. When set to `true`, the engine will run in eager mode without using CUDA graphs or other compilation optimizations. Currently, vLLM-Omni only supports eager mode.
+
+Default: `true`
+
+#### `engine_args.trust_remote_code`
+
+Whether to trust remote code when loading models from Hugging Face. This is required for models that use custom code in their configuration files. Set to `true` when loading models that require custom model implementations.
+
+Default: `true`
+
+#### `engine_args.engine_output_type`
+
+Specifies the type of output produced by this stage's engine. This determines what kind of data flows to downstream stages. Possible values include `latent` (hidden states), `text` (tokenized text), and `audio` (audio waveforms). When set to `latent`, the stage outputs latent hidden states in addition to token IDs, which are consumed by downstream stages.
+
+Default: `latent`
+
+#### `engine_args.enable_prefix_caching`
+
+Whether to enable prefix caching for this stage. Prefix caching can improve performance by caching KV cache for common prompt prefixes. However, for requests that output hidden states (when `engine_output_type` is `latent`), prefix caching is not currently supported and should be set to `false`.
+
+Default: `false`
+
+### `is_comprehension`
+
+Whether this stage is a text or multimodal comprehension module. When set to `true`, the stage acts as a comprehension module that processes input text or multimodal content. If this is the first comprehension stage, `AsyncOmniLLM` will use its tokenizer as the default tokenizer for the entire pipeline.
+
+Default: `true`
+
+### `final_output`
+
+Whether this stage produces output that is part of the final outputs returned to the user. When set to `false`, the stage only works as an intermediate stage, processing data that flows to downstream stages but not contributing directly to the final response.
+
+Default: `true`
+
+### `final_output_type`
+
+The type of final output produced by this stage. This specifies what format the output will be in when returned to the user. Currently supported values are `text` (for text generation) and `audio` (for audio generation).
+
+Default: `text`
+
+### `default_sampling_params`
+
+Default sampling parameters for this stage. These parameters control the generation behavior and align with vLLM's sampling parameter semantics. These defaults are used when no explicit sampling parameters are provided in the request.
+
+#### `default_sampling_params.temperature`
+
+Sampling temperature for controlling randomness. Lower values (e.g., 0.0) make the output more deterministic and focused, while higher values increase randomness.
+
+Default: `0.0`
+
+#### `default_sampling_params.top_p`
+
+Nucleus sampling parameter. Only tokens with cumulative probability mass up to `top_p` are considered. This helps filter out low-probability tokens while maintaining diversity.
+
+Default: `1.0`
+
+#### `default_sampling_params.top_k`
+
+Top-k sampling parameter. Only the top `k` most likely tokens are considered. Set to `-1` to disable top-k filtering and consider all tokens.
+
+Default: `-1`
+
+#### `default_sampling_params.max_tokens`
+
+Maximum number of tokens to generate in this stage. This limits the length of the output sequence.
+
+Default: `2048`
+
+#### `default_sampling_params.seed`
+
+Random seed for reproducible generation. When set, the random number generator will be initialized with this seed to ensure consistent outputs across runs.
+
+Default: `42`
+
+#### `default_sampling_params.detokenize`
+
+Whether to detokenize the output tokens into text. When set to `true`, token IDs are converted back to readable text strings.
+
+Default: `True`
+
+#### `default_sampling_params.repetition_penalty`
+
+Penalty applied to tokens that have already appeared in the generated sequence. Values greater than 1.0 discourage repetition, while values less than 1.0 encourage it. A value of 1.0 applies no penalty.
+
+Default: `1.1`

docs/configuration/stage_configs/qwen2_5_omni.yaml

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+# stage config for running qwen2.5-omni with architecture of OmniLLM.
+stage_args:
+  - stage_id: 0
+    runtime:
+      process: true            # Run this stage in a separate process
+      devices: "0"            # Visible devices for this stage (CUDA_VISIBLE_DEVICES/torch.cuda.set_device)
+      max_batch_size: 1
+    engine_args:
+      model_stage: thinker
+      model_arch: Qwen2_5OmniForConditionalGeneration
+      worker_cls: vllm_omni.worker.gpu_ar_worker.GPUARWorker
+      scheduler_cls: vllm_omni.core.sched.scheduler.OmniScheduler
+      gpu_memory_utilization: 0.8
+      enforce_eager: true  # Now we only support eager mode
+      trust_remote_code: true
+      engine_output_type: latent
+      enable_prefix_caching: false
+    is_comprehension: true
+    final_output: true
+    final_output_type: text
+    default_sampling_params:
+      temperature: 0.0
+      top_p: 1.0
+      top_k: -1
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.1
+  - stage_id: 1
+    runtime:
+      process: true
+      devices: "1"
+      max_batch_size: 3
+    engine_args:
+      model_stage: talker
+      model_arch: Qwen2_5OmniForConditionalGeneration
+      worker_cls: vllm_omni.worker.gpu_ar_worker.GPUARWorker
+      scheduler_cls: vllm_omni.core.sched.scheduler.OmniScheduler
+      gpu_memory_utilization: 0.8
+      enforce_eager: true
+      trust_remote_code: true
+      enable_prefix_caching: false
+      engine_output_type: latent
+    engine_input_source: [0]
+    custom_process_input_func: vllm_omni.model_executor.stage_input_processors.qwen2_5_omni.thinker2talker
+    default_sampling_params:
+      temperature: 0.9
+      top_p: 0.8
+      top_k: 40
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.05
+      stop_token_ids: [8294]
+  - stage_id: 2
+    runtime:
+      process: true
+      devices: "0"            # Example: use a different GPU than the previous stage; use "0" if single GPU
+      max_batch_size: 1
+    engine_args:
+      model_stage: code2wav
+      model_arch: Qwen2_5OmniForConditionalGeneration
+      worker_cls: vllm_omni.worker.gpu_diffusion_worker.GPUDiffusionWorker
+      scheduler_cls: vllm_omni.core.sched.diffusion_scheduler.DiffusionScheduler
+      gpu_memory_utilization: 0.15
+      enforce_eager: true
+      trust_remote_code: true
+      enable_prefix_caching: false
+      engine_output_type: audio
+    engine_input_source: [1]
+    final_output: true
+    final_output_type: audio
+    default_sampling_params:
+      temperature: 0.0
+      top_p: 1.0
+      top_k: -1
+      max_tokens: 2048
+      seed: 42
+      detokenize: True
+      repetition_penalty: 1.1
+
+# Top-level runtime config (concise): default windows and stage edges
+runtime:
+  enabled: true
+  defaults:
+    window_size: -1             # Simplified: trigger downstream only after full upstream completion
+    max_inflight: 1             # Simplified: process serially within each stage
+  edges:
+    - from: 0                   # thinker → talker: trigger only after receiving full input (-1)
+      to: 1
+      window_size: -1
+    - from: 1                   # talker → code2wav: trigger only after receiving full input (-1)
+      to: 2
+      window_size: -1