vllm-cpu 0.20.1

A high-throughput and memory-efficient inference and serving engine for LLMs

CPU-Optimized vLLM: Easy, Fast LLM Inference Without a GPU

Unified CPU wheel with automatic ISA detection at runtime (AVX2, AVX-512, VNNI, BF16, AMX, NEON, FP16, DOTPROD)

This is an independent, community-maintained package — not affiliated with or funded by the vLLM project, its sister concerns, or any hardware vendors. The first successful unification of different CPU ISAs (AVX2, AVX-512, VNNI, BF16, AMX) into a single wheel was done by Mekayel Anik, for the benefit of the community.

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Overview

vllm-cpu provides unified CPU wheels for vLLM on PyPI. One package, one pip install, automatic CPU instruction set detection.

Why CPU inference?

• No expensive GPU required
• Run LLMs on any server, laptop, or edge device
• Lower power consumption and operational costs
• Ideal for development, testing, and moderate-scale deployments
• ARM64 support for AWS Graviton 3+, Ampere Altra, and other aarch64 servers (NEON + BF16/DOTPROD)

Key Features:

• pip3 install vllm-cpu -- no manual URLs or GitHub Release downloads
• Built with manylinux_2_28 for broad compatibility (Debian 10+, Ubuntu 18.04+)
• Stable ABI (cp38-abi3) -- one wheel for Python 3.10+
• Automatic ISA detection at runtime (AVX2/AVX-512/AMX on x86, NEON/BF16 on ARM)

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Table of Contents

• Quick Start
• Installation
• Supported CPU Instructions
• CPU Compatibility Guide
• Usage Examples
• Performance Tips
• Environment Variables
• Supported Models
• Framework Integrations
• Version Support
• Troubleshooting
• Links & Resources

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Quick Start

1. Install

pip3 install vllm-cpu

2. Run your first model

from vllm import LLM, SamplingParams

llm = LLM(model="Qwen/Qwen3-0.6B", dtype="bfloat16")
outputs = llm.generate(["Hello, my name is"], SamplingParams(max_tokens=50))
print(outputs[0].outputs[0].text)

3. Or start an OpenAI-compatible server

vllm serve Qwen/Qwen3-0.6B --dtype auto

curl http://localhost:8000/v1/completions \
  -H "Content-Type: application/json" \
  -d '{"model": "Qwen/Qwen3-0.6B", "prompt": "The future of AI is", "max_tokens": 128}'

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Installation

Prerequisites

Requirement	Details
Python	3.10+ (stable ABI -- one wheel for all versions)
OS	Linux (glibc 2.28+) -- Debian 10+, Ubuntu 18.04+, RHEL 8+, Amazon Linux 2023+
CPU	x86_64 with AVX2 (minimum) or AVX-512 (optimal), or aarch64 with NEON (BF16 recommended)
Windows	Use WSL2 (Windows Subsystem for Linux)

pip

pip3 install vllm-cpu                # Latest
pip3 install vllm-cpu==0.17.0        # Specific version

uv (faster)

uv pip install vllm-cpu

Virtual environment (recommended)

python -m venv vllm-env && source vllm-env/bin/activate
pip3 install vllm-cpu

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Supported CPU Instructions

The unified wheel automatically detects and uses the best available instruction set at import time. No configuration needed.

	CPU Feature	Benefit
Baseline	AVX2	256-bit SIMD -- works on all modern x86_64
Faster	AVX512	512-bit vectors -- 2x wider than AVX2
Faster	AVX512-VNNI	INT8 multiply-accumulate for quantized inference
Faster	AVX512-BF16	Native BFloat16 -- half the memory of FP32
Fastest	AMX-BF16	Tile-based matrix acceleration (Sapphire Rapids+)
ARM	aarch64 NEON	ARM SIMD baseline for all aarch64
ARM	aarch64 FP16	Half-precision float (always enabled)
ARM	aarch64 DOTPROD	INT8 dot product acceleration (always enabled)
ARM	aarch64 BF16	Native BFloat16 (Graviton 3+, Ampere Altra+)

How it works: The wheel ships _C.so (AVX512+BF16+VNNI+AMX) and _C_AVX2.so (AVX2 fallback). At import vllm, the correct .so is loaded once based on CPU capabilities. Zero runtime overhead.

Check your CPU

# x86_64
lscpu | grep -E "avx512|vnni|bf16|amx"

# aarch64
cat /proc/cpuinfo | grep -i "features" | head -1
# Look for: asimd (NEON), bf16

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CPU Compatibility Guide

Intel

Generation	Example CPUs	ISA Used
Haswell+ (2013)	Core i5/i7 4th--11th Gen	AVX2
Skylake-X (2017)	Core i9-7900X, Xeon W-2195	AVX512
Cascade Lake (2019)	Xeon Platinum 8280	AVX512 + VNNI
Cooper Lake (2020)	Xeon Platinum 8380H	AVX512 + BF16
Sapphire Rapids+ (2023)	Xeon w9-3495X, 4th/5th/6th Gen Xeon	AVX512 + AMX
Consumer 12th--14th Gen	Core i5/i7/i9 (Alder Lake+)	AVX2

AMD

Generation	Example CPUs	ISA Used
Zen 2/3 (2019--2020)	Ryzen 3000--5000, EPYC 7002--7003	AVX2
Zen 4+ (2022+)	Ryzen 7000+, EPYC 9004+	AVX512 + BF16

ARM

Platform	Example	ISA Used
AWS Graviton 2/3/4	c7g, m7g instances	NEON
Apple Silicon	M1--M4 (via Docker/Lima)	NEON
Ampere Altra	Cloud instances	NEON

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Usage Examples

Batch Processing

from vllm import LLM, SamplingParams

llm = LLM(
    model="google/gemma-3-1b-it",
    dtype="bfloat16",
    max_model_len=2048
)

prompts = [
    "Explain quantum computing in simple terms:",
    "Write a Python function to reverse a string:",
]

outputs = llm.generate(prompts, SamplingParams(temperature=0.7, max_tokens=256))
for output in outputs:
    print(f"Prompt: {output.prompt}")
    print(f"Generated: {output.outputs[0].text}\n")

OpenAI Python Client

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8000/v1", api_key="not-needed")

response = client.chat.completions.create(
    model="Qwen/Qwen3-4B",
    messages=[{"role": "user", "content": "What is the capital of France?"}]
)
print(response.choices[0].message.content)

cURL

curl http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{"model": "Qwen/Qwen3-4B",
       "messages": [{"role": "user", "content": "Hello!"}]}'

---

Performance Tips

1. Use TCMalloc (strongly recommended)

Official recommendation: vLLM strongly recommends TCMalloc for high-performance memory allocation and better cache locality.

# Install
sudo apt install libtcmalloc-minimal4        # Debian/Ubuntu
sudo dnf install gperftools-libs              # RHEL/Fedora

# Preload
export LD_PRELOAD=$(find /usr -name "libtcmalloc_minimal.so*" | head -1)
vllm serve your-model --dtype auto

2. Set thread count to physical cores

Tip: Disable hyper-threading on bare-metal for best performance. Reserve 1--2 cores for the HTTP serving framework.

export OMP_NUM_THREADS=16                     # Physical core count
export MKL_NUM_THREADS=16
export VLLM_CPU_OMP_THREADS_BIND=0-13         # Pin inference threads
export VLLM_CPU_NUM_OF_RESERVED_CPU=2          # Reserve for HTTP serving

3. Use BFloat16

Note: Float16 is unstable on CPU. Always use bfloat16.

llm = LLM(model="your-model", dtype="bfloat16")

4. NUMA optimization (multi-socket systems)

# Simple: bind to one NUMA node
numactl --cpunodebind=0 --membind=0 python your_script.py

# Advanced: Tensor Parallel across NUMA nodes
VLLM_CPU_OMP_THREADS_BIND=0-31|32-63 vllm serve your-model \
  --dtype auto --tensor-parallel-size 2

5. Tune KV cache

export VLLM_CPU_KVCACHE_SPACE=40              # 40 GB for KV cache

6. SGL kernels (x86, experimental)

export VLLM_CPU_SGL_KERNEL=1                  # Low-latency online serving

7. Quantized models

llm = LLM(model="Qwen/Qwen3-8B-GPTQ-Int4", quantization="gptq")

Memory Estimation

Model Size	bfloat16	GPTQ INT4
1B params	~4 GB	~2 GB
7B params	~16 GB	~6 GB
13B params	~28 GB	~10 GB
70B params	~140 GB	~40 GB

Add 2--8 GB for KV cache depending on VLLM_CPU_KVCACHE_SPACE and context length.

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Environment Variables

Variable	Description	Default
VLLM_CPU_KVCACHE_SPACE	KV cache size in GB (larger = more concurrent requests)	0 (auto)
VLLM_CPU_OMP_THREADS_BIND	CPU core binding (0-31, auto, or nobind)	auto
VLLM_CPU_NUM_OF_RESERVED_CPU	Cores reserved for HTTP serving (when bind=auto)	0
VLLM_CPU_SGL_KERNEL	Small-batch optimized kernels (x86, experimental)	0
OMP_NUM_THREADS	OpenMP thread count	All cores
MKL_NUM_THREADS	Intel MKL thread count	All cores
LD_PRELOAD	Preload TCMalloc for better memory performance	--
HF_TOKEN	Hugging Face access token	--
HF_HOME	Hugging Face cache directory	~/.cache/huggingface

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Supported Models

vLLM supports 100+ model architectures including:

Category	Models
LLMs	Llama 2/3/3.1/3.2, Mistral, Mixtral, Qwen 2/2.5/3, Phi-2/3/4, Gemma 2/3, DeepSeek V2/V3/R1
Code	CodeLlama, DeepSeek-Coder, StarCoder 1/2, CodeGemma, Qwen2.5-Coder
Embedding	E5-Mistral, GTE, BGE, Nomic-Embed, Jina
Multimodal	LLaVA, Qwen-VL, Qwen2.5-VL, InternVL, Pixtral, MiniCPM-V
MoE	Mixtral 8x7B/8x22B, DeepSeek-MoE, Qwen-MoE, DBRX

Full list: vLLM Supported Models

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Framework Integrations

vLLM's server is fully OpenAI API-compatible. Any client that supports base_url override works out of the box.

LangChain

from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    base_url="http://localhost:8000/v1",
    api_key="not-needed",
    model="Qwen/Qwen3-4B"
)
response = llm.invoke("Explain machine learning in simple terms")

LlamaIndex

from llama_index.llms.openai_like import OpenAILike

llm = OpenAILike(
    api_base="http://localhost:8000/v1",
    api_key="not-needed",
    model="Qwen/Qwen3-4B"
)
response = llm.complete("What is the capital of France?")

Also works with: Semantic Kernel, AutoGen, CrewAI, Haystack, and any OpenAI-compatible SDK.

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Version Support

Version Range	Strategy	Status
v0.17.0+	Unified CPU wheel (this package)	Active
v0.8.5 -- v0.15.x	Legacy 5-variant wheels	Archived on PyPI

Legacy packages (vllm-cpu-avx512, vllm-cpu-avx512vnni, vllm-cpu-avx512bf16, vllm-cpu-amxbf16) remain on PyPI for older vLLM versions but are no longer updated.

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Troubleshooting

Illegal Instruction Error

The unified wheel auto-detects CPU capabilities. If you still see this:

lscpu | grep -E "avx512|vnni|bf16|amx"    # Check supported features

If no AVX2 flags appear, your CPU is too old for vLLM CPU inference.

Out of Memory (OOM)

llm = LLM(model="your-model", max_model_len=2048, dtype="bfloat16")

export VLLM_CPU_KVCACHE_SPACE=2               # Reduce KV cache

Slow Performance Checklist

Check	Command / Fix
TCMalloc loaded?	echo $LD_PRELOAD -- should show libtcmalloc
Thread count correct?	echo $OMP_NUM_THREADS -- should equal physical cores
Hyper-threading disabled?	Recommended for bare-metal
Cross-NUMA access?	Use VLLM_CPU_OMP_THREADS_BIND to pin to one node
Using bfloat16?	Float16 is unstable on CPU -- always use dtype="bfloat16"

Multiple vLLM Packages Conflict

pip3 uninstall vllm vllm-cpu vllm-cpu-avx512 vllm-cpu-avx512vnni vllm-cpu-avx512bf16 vllm-cpu-amxbf16 -y
pip3 install vllm-cpu

RuntimeError: Failed to infer device type

For legacy versions (v0.8.5--v0.15.x), use .post2 releases:

pip3 install vllm-cpu==0.12.0.post2

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Links & Resources

	Resource	Link
Source	GitHub Repository	github.com/MekayelAnik/vllm-cpu
Docker	Docker Hub Images	hub.docker.com/r/mekayelanik/vllm-cpu
GHCR	GitHub Container Registry	ghcr.io/mekayelanik/vllm-cpu
Docs	vLLM Documentation	docs.vllm.ai
Upstream	vLLM Project	github.com/vllm-project/vllm
Issues	Report a Bug	github.com/MekayelAnik/vllm-cpu/issues
Releases	Changelog	GitHub Releases

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License: GPL-3.0 | Upstream: Apache-2.0

_{Built from vLLM, originally developed at Sky Computing Lab, UC Berkeley}