In the example above, the KV cache in the first block can be uniquely identified with the token “A gentle breeze stirred”. The third block can be uniquely identified with the tokens in the block “laughed in the distance”, along with the prefix tokens “A gentle breeze stirred the leaves as children”. Therefore, we can build the block hash of `hash(tuple[components])`, where components are:
* Parent hash value: The hash value of the parent hash block.
* Block tokens: A tuple of tokens in this block. The reason to include the exact tokens is to reduce potential hash value collision.
* Block tokens: A tuple of tokens in this block. The reason to include the exact tokens is to reduce potential hash value collision.
* Extra hashes: Other values required to make this block unique, such as LoRA IDs and multi-modality input hashes (see the example below).
Note 1: We only cache full blocks.
> **Note 1:** We only cache full blocks.
Note 2: The above hash key structure is not 100% collision free. Theoretically it’s still possible for the different prefix tokens to have the same hash value, but this should be nearly impossible to happen. Of course, contributions are welcome if you have an awesome idea to eliminate collusion entirely.
> **Note 2:** The above hash key structure is not 100% collision free. Theoretically it’s still possible for the different prefix tokens to have the same hash value. To avoid any hash collisions **in a multi-tenant setup, we advise to use SHA256** as hash function instead of the default builtin hash.
SHA256 is supported since vLLM v0.8.3 and must be enabled with a command line argument. It comes with a performance impact of about 100-200ns per token (~6ms for 50k tokens of context).
**A hashing example with multi-modality inputs**
In this example, we illustrate how prefix caching works with multi-modality inputs (e.g., images). Assuming we have a request with the following messages:
Quantization can effectively reduce memory and bandwidth usage, accelerate computation and improve
throughput while with minimal accuracy loss. vLLM can leverage [Quark](https://quark.docs.amd.com/latest/),
the flexible and powerful quantization toolkit, to produce performant quantized models to run on AMD GPUs. Quark has specialized support for quantizing large language models with weight,
activation and kv-cache quantization and cutting-edge quantization algorithms like
AWQ, GPTQ, Rotation and SmoothQuant.
## Quark Installation
Before quantizing models, you need to install Quark. The latest release of Quark can be installed with pip:
```console
pip install amd-quark
```
You can refer to [Quark installation guide](https://quark.docs.amd.com/latest/install.html)
for more installation details.
## Quantization Process
After installing Quark, we will use an example to illustrate how to use Quark.
The Quark quantization process can be listed for 5 steps as below:
vLLM offers support for reasoning models like [DeepSeek R1](https://huggingface.co/deepseek-ai/DeepSeek-R1), which are designed to generate outputs containing both reasoning steps and final conclusions.
Reasoning models return a additional `reasoning_content` field in their outputs, which contains the reasoning steps that led to the final conclusion. This field is not present in the outputs of other models.
Reasoning models return an additional `reasoning_content` field in their outputs, which contains the reasoning steps that led to the final conclusion. This field is not present in the outputs of other models.
## Supported Models
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@@ -14,6 +14,9 @@ vLLM currently supports the following reasoning models:
@@ -131,7 +136,14 @@ Remember to check whether the `reasoning_content` exists in the response before
## Structured output
The reasoning content is also available in the structured output. The structured output engine like `xgrammar` will use the reasoning content to generate structured output.
The reasoning content is also available in the structured output. The structured output engine like `xgrammar` will use the reasoning content to generate structured output. It is only supported in v0 engine now.
Note: Please use `--speculative_config` to set all configurations related to speculative decoding. The previous method of specifying the model through `--speculative_model` and adding related parameters (e.g., `--num_speculative_tokens`) separately will be deprecated in the next release.
Note: Please use `--speculative_config` to set all configurations related to speculative decoding. The previous method of specifying the model through `--speculative_model` and adding related parameters (e.g., `--num_speculative_tokens`) separately has been deprecated now.
vLLM currently supports named function calling, as well as the `auto` and `none` options for the `tool_choice` field in the chat completion API. The `tool_choice` option `required` is **not yet supported** but [on the roadmap](gh-issue:13002).
vLLM currently supports named function calling, as well as the `auto`, `required` (as of `vllm>=0.8.3`) and `none` options for the `tool_choice` field in the chat completion API.
## Quickstart
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@@ -91,6 +91,12 @@ For best results, we recommend ensuring that the expected output format / schema
To use a named function, you need to define the functions in the `tools` parameter of the chat completion request, and
specify the `name` of one of the tools in the `tool_choice` parameter of the chat completion request.
## Required Function Calling
vLLM supports the `tool_choice='required'` option in the chat completion API. Similar to the named function calling, it also uses guided decoding, so this is enabled by default and will work with any supported model. The required guided decoding features (JSON schema with `anyOf`) are currently only supported in the V0 engine with the guided decoding backend `outlines`. However, support for alternative decoding backends are on the [roadmap](https://docs.vllm.ai/en/latest/getting_started/v1_user_guide.html#feature-model) for the V1 engine.
When tool_choice='required' is set, the model is guaranteed to generate one or more tool calls based on the specified tool list in the `tools` parameter. The number of tool calls depends on the user's query. The output format strictly follows the schema defined in the `tools` parameter.
## Automatic Function Calling
To enable this feature, you should set the following flags:
- Decouple the HTTP serving components from the inference components. In a GPU backend configuration, the HTTP serving and tokenization tasks operate on the CPU, while inference runs on the GPU, which typically does not pose a problem. However, in a CPU-based setup, the HTTP serving and tokenization can cause significant context switching and reduced cache efficiency. Therefore, it is strongly recommended to segregate these two components for improved performance.
- On CPU based setup with NUMA enabled, the memory access performance may be largely impacted by the [topology](https://github.com/intel/intel-extension-for-pytorch/blob/main/docs/tutorials/performance_tuning/tuning_guide.inc.md#non-uniform-memory-access-numa). For NUMA architecture, two optimizations are to recommended: Tensor Parallel or Data Parallel.
- On CPU based setup with NUMA enabled, the memory access performance may be largely impacted by the [topology](https://github.com/intel/intel-extension-for-pytorch/blob/main/docs/tutorials/performance_tuning/tuning_guide.inc.md#non-uniform-memory-access-numa). For NUMA architecture, Tensor Parallel is a option for better performance.
-Using Tensor Parallel for a latency constraints deployment: following GPU backend design, a Megatron-LM's parallel algorithm will be used to shard the model, based on the number of NUMA nodes (e.g. TP = 2 for a two NUMA node system). With [TP feature on CPU](gh-pr:6125) merged, Tensor Parallel is supported for serving and offline inferencing. In general each NUMA node is treated as one GPU card. Below is the example script to enable Tensor Parallel = 2 for serving:
- Tensor Parallel is supported for serving and offline inferencing. In general each NUMA node is treated as one GPU card. Below is the example script to enable Tensor Parallel = 2 for serving:
- Using Data Parallel for maximum throughput: to launch an LLM serving endpoint on each NUMA node along with one additional load balancer to dispatch the requests to those endpoints. Common solutions like [Nginx](#nginxloadbalancer) or HAProxy are recommended. Anyscale Ray project provides the feature on LLM [serving](https://docs.ray.io/en/latest/serve/index.html). Here is the example to setup a scalable LLM serving with [Ray Serve](https://github.com/intel/llm-on-ray/blob/main/docs/setup.inc.md).
- For each thread id list in `VLLM_CPU_OMP_THREADS_BIND`, users should guarantee threads in the list belong to a same NUMA node.
- Meanwhile, users should also take care of memory capacity of each NUMA node. The memory usage of each TP rank is the sum of `weight shard size` and `VLLM_CPU_KVCACHE_SPACE`, if it exceeds the capacity of a single NUMA node, TP worker will be killed due to out-of-memory.
1. Install [Triton flash attention for ROCm](https://github.com/ROCm/triton)
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@@ -123,7 +123,7 @@ Building the Docker image from source is the recommended way to use vLLM with RO
#### (Optional) Build an image with ROCm software stack
Build a docker image from <gh-file:Dockerfile.rocm_base> which setup ROCm software stack needed by the vLLM.
Build a docker image from <gh-file:docker/Dockerfile.rocm_base> which setup ROCm software stack needed by the vLLM.
**This step is optional as this rocm_base image is usually prebuilt and store at [Docker Hub](https://hub.docker.com/r/rocm/vllm-dev) under tag `rocm/vllm-dev:base` to speed up user experience.**
If you choose to build this rocm_base image yourself, the steps are as follows.
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@@ -140,12 +140,12 @@ It is important that the user kicks off the docker build using buildkit. Either
To build vllm on ROCm 6.3 for MI200 and MI300 series, you can use the default:
First, build a docker image from <gh-file:Dockerfile.rocm> and launch a docker container from the image.
First, build a docker image from <gh-file:docker/Dockerfile.rocm> and launch a docker container from the image.
It is important that the user kicks off the docker build using buildkit. Either the user put `DOCKER_BUILDKIT=1` as environment variable when calling docker build command, or the user needs to setup buildkit in the docker daemon configuration /etc/docker/daemon.json as follows and restart the daemon:
```console
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@@ -156,10 +156,10 @@ It is important that the user kicks off the docker build using buildkit. Either
}
```
<gh-file:Dockerfile.rocm> uses ROCm 6.3 by default, but also supports ROCm 5.7, 6.0, 6.1, and 6.2, in older vLLM branches.
<gh-file:docker/Dockerfile.rocm> uses ROCm 6.3 by default, but also supports ROCm 5.7, 6.0, 6.1, and 6.2, in older vLLM branches.
It provides flexibility to customize the build of docker image using the following arguments:
-`BASE_IMAGE`: specifies the base image used when running `docker build`. The default value `rocm/vllm-dev:base` is an image published and maintained by AMD. It is being built using <gh-file:Dockerfile.rocm_base>
-`BASE_IMAGE`: specifies the base image used when running `docker build`. The default value `rocm/vllm-dev:base` is an image published and maintained by AMD. It is being built using <gh-file:docker/Dockerfile.rocm_base>
-`USE_CYTHON`: An option to run cython compilation on a subset of python files upon docker build
-`BUILD_RPD`: Include RocmProfileData profiling tool in the image
-`ARG_PYTORCH_ROCM_ARCH`: Allows to override the gfx architecture values from the base docker image
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@@ -169,13 +169,13 @@ Their values can be passed in when running `docker build` with `--build-arg` opt
To build vllm on ROCm 6.3 for MI200 and MI300 series, you can use the default:
@@ -208,5 +208,5 @@ Currently, vLLM supports multiple backends for efficient Attention computation a
If desired, you can also manually set the backend of your choice by configuring the environment variable `VLLM_ATTENTION_BACKEND` to one of the following options: `FLASH_ATTN`, `FLASHINFER` or `XFORMERS`.
```{attention}
There are no pre-built vllm wheels containing Flash Infer, so you must install it in your environment first. Refer to the [Flash Infer official docs](https://docs.flashinfer.ai/) or see [Dockerfile](https://github.com/vllm-project/vllm/blob/main/Dockerfile) for instructions on how to install it.
There are no pre-built vllm wheels containing Flash Infer, so you must install it in your environment first. Refer to the [Flash Infer official docs](https://docs.flashinfer.ai/) or see <gh-file:docker/Dockerfile> for instructions on how to install it.
@@ -26,6 +26,14 @@ To isolate the model downloading and loading issue, you can use the `--load-form
If the model is too large to fit in a single GPU, you will get an out-of-memory (OOM) error. Consider [using tensor parallelism](#distributed-serving) to split the model across multiple GPUs. In that case, every process will read the whole model and split it into chunks, which makes the disk reading time even longer (proportional to the size of tensor parallelism). You can convert the model checkpoint to a sharded checkpoint using <gh-file:examples/offline_inference/save_sharded_state.py>. The conversion process might take some time, but later you can load the sharded checkpoint much faster. The model loading time should remain constant regardless of the size of tensor parallelism.
## Generation quality changed
In v0.8.0, the source of default sampling parameters was changed in <gh-pr:12622>. Prior to v0.8.0, the default sampling parameters came from vLLM's set of neutral defaults. From v0.8.0 onwards, the default sampling parameters come from the `generation_config.json` provided by the model creator.
In most cases, this should lead to higher quality responses, because the model creator is likely to know which sampling parameters are best for their model. However, in some cases the defaults provided by the model creator can lead to degraded performance.
You can check if this is happening by trying the old defaults with `--generation-config vllm` for online and `generation_config="vllm"` for offline. If, after trying this, your generation quality improves we would recommend continuing to use the vLLM defaults and petition the model creator on <https://huggingface.co> to update their default `generation_config.json` so that it produces better quality generations.
## Enable more logging
If other strategies don't solve the problem, it's likely that the vLLM instance is stuck somewhere. You can use the following environment variables to help debug the issue:
-**Spec Decode**: Currently, only ngram-based spec decode is supported in V1. There
will be follow-up work to support other types of spec decode (e.g., see [PR #13933](https://github.com/vllm-project/vllm/pull/13933)). We will prioritize the support for Eagle, MTP compared to draft model based spec decode.
#### Features to Be Supported
-**Multimodal Models**: V1 is almost fully compatible with V0 except that interleaved modality input is not supported yet.
See [here](https://github.com/orgs/vllm-project/projects/8) for the status of upcoming features and optimizations.
-**FP8 KV Cache**: While vLLM V1 introduces new FP8 kernels for model weight quantization, support for an FP8 key–value cache is not yet available. Users must continue using FP16 (or other supported precisions) for the KV cache.
#### Features to Be Supported
-**Structured Output Alternative Backends**: Structured output alternative backends (outlines, guidance) support is planned. V1 currently
supports only the `xgrammar:no_fallback` mode, meaning that it will error out if the output schema is unsupported by xgrammar.