We host regular meetups in San Francisco Bay Area every 2 months. We will share the project updates from the vLLM team and have guest speakers from the industry to share their experience and insights. Please find the materials of our previous meetups below:
- `The fourth vLLM meetup <https://lu.ma/agivllm>`__, with Cloudflare and BentoML, June 11th 2024. `[Slides] <https://docs.google.com/presentation/d/1iJ8o7V2bQEi0BFEljLTwc5G1S10_Rhv3beed5oB0NJ4/edit?usp=sharing>`__
- `The third vLLM meetup <https://robloxandvllmmeetup2024.splashthat.com/>`__, with Roblox, April 2nd 2024. `[Slides] <https://docs.google.com/presentation/d/1A--47JAK4BJ39t954HyTkvtfwn0fkqtsL8NGFuslReM/edit?usp=sharing>`__
- `The second vLLM meetup <https://lu.ma/ygxbpzhl>`__, with IBM Research, January 31st 2024. `[Slides] <https://docs.google.com/presentation/d/12mI2sKABnUw5RBWXDYY-HtHth4iMSNcEoQ10jDQbxgA/edit?usp=sharing>`__ `[Video (vLLM Update)] <https://youtu.be/Y0C-DUvEnZQ>`__ `[Video (IBM Research & torch.compile)] <https://youtu.be/m0dMtFLI-dg>`__
- `The first vLLM meetup <https://lu.ma/first-vllm-meetup>`__, with a16z, October 5th 2023. `[Slides] <https://docs.google.com/presentation/d/1QL-XPFXiFpDBh86DbEegFXBXFXjix4v032GhShbKf3s/edit?usp=sharing>`__
* Instruction set architecture (ISA) requirement: AVX512 is required.
.. _cpu_backend_quick_start_dockerfile:
...
...
@@ -41,7 +42,7 @@ Quick start using Dockerfile
Build from source
-----------------
- First, install required compiler. We recommend to use ``gcc/g++ >= 12.3.0`` as the default compiler to avoid potential problems. For example, on Ubuntu 22.4, you can run:
- First, install recommended compiler. We recommend to use ``gcc/g++ >= 12.3.0`` as the default compiler to avoid potential problems. For example, on Ubuntu 22.4, you can run:
.. code-block:: console
...
...
@@ -70,6 +71,15 @@ Build from source
- If you want to force enable AVX512_BF16 for the cross-compilation, please set environment variable VLLM_CPU_AVX512BF16=1 before the building.
.. _ipex_guidance:
Intel Extension for PyTorch
---------------------------
- `Intel Extension for PyTorch (IPEX) <https://github.com/intel/intel-extension-for-pytorch>`_ extends PyTorch with up-to-date features optimizations for an extra performance boost on Intel hardware.
- IPEX after the ``2.3.0`` can be enabled in the CPU backend by default if it is installed.
.. _cpu_backend_performance_tips:
Performance tips
...
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@@ -77,6 +87,15 @@ Performance tips
- vLLM CPU backend uses environment variable ``VLLM_CPU_KVCACHE_SPACE`` to specify the KV Cache size (e.g, ``VLLM_CPU_KVCACHE_SPACE=40`` means 40 GB space for KV cache), larger setting will allow vLLM running more requests in parallel. This parameter should be set based on the hardware configuration and memory management pattern of users.
- We highly recommend to use TCMalloc for high performance memory allocation and better cache locality. For example, on Ubuntu 22.4, you can run:
$ find / -name *libtcmalloc* # find the dynamic link library path
$ export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libtcmalloc_minimal.so.4:$LD_PRELOAD # prepend the library to LD_PRELOAD
$ python examples/offline_inference.py # run vLLM
- vLLM CPU backend uses OpenMP for thread-parallel computation. If you want the best performance on CPU, it will be very critical to isolate CPU cores for OpenMP threads with other thread pools (like web-service event-loop), to avoid CPU oversubscription.
- If using vLLM CPU backend on a bare-metal machine, it is recommended to disable the hyper-threading.
When an vLLM instance hangs or crashes, it is very difficult to debug the issue. But wait a minute, it is also possible that vLLM is doing something that indeed takes a long time:
- Downloading a model: do you have the model already downloaded in your disk? If not, vLLM will download the model from the internet, which can take a long time. Be sure to check the internet connection. It would be better to download the model first using `huggingfacecli <https://huggingface.co/docs/huggingface_hub/en/guides/cli>`_ and then use the local path to the model. This way, you can isolate the issue.
- Loading the model from disk: if the model is large, it can take a long time to load the model from disk. Please take care of the location you store the model. Some clusters have shared filesystems across nodes, e.g. distributed filesystem or network filesystem, which can be slow. It would be better to store the model in a local disk. In addition, please also watch the CPU memory usage. When the model is too large, it might take much CPU memory, which can slow down the operating system because it needs to frequently swap memory between the disk and the memory.
- Tensor parallel inference: if the model is too large to fit in a single GPU, you might want to use tensor parallelism 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 `the provided script <https://docs.vllm.ai/en/latest/getting_started/examples/save_sharded_state.html>`_ . 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.
- **Downloading a model**: Do you have the model already downloaded in your disk? If not, vLLM will download the model from the internet, which can take a long time. Be sure to check the internet connection. It would be better to download the model first using `huggingface-cli <https://huggingface.co/docs/huggingface_hub/en/guides/cli>`_ and then use the local path to the model. This way, you can isolate the issue.
- **Loading the model from disk**: If the model is large, it can take a long time to load the model from disk. Please take care of the location you store the model. Some clusters have shared filesystems across nodes, e.g. distributed filesystem or network filesystem, which can be slow. It would be better to store the model in a local disk. In addition, please also watch the CPU memory usage. When the model is too large, it might take much CPU memory, which can slow down the operating system because it needs to frequently swap memory between the disk and the memory.
- **Tensor parallel inference**: If the model is too large to fit in a single GPU, you might want to use tensor parallelism 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 `the provided script <https://docs.vllm.ai/en/latest/getting_started/examples/save_sharded_state.html>`_ . 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.
If you already take care of the above issues, and the vLLM instance still hangs, with CPU and GPU utilization at near zero, it is likely that the vLLM instance is stuck somewhere. Here are some tips to help debug the issue:
If you have already taken care of the above issues, but the vLLM instance still hangs, with CPU and GPU utilization at near zero, it is likely that the vLLM instance is stuck somewhere. Here are some tips to help debug the issue:
- Set the environment variable ``export VLLM_LOGGING_LEVEL=DEBUG`` to turn on more logging.
- Set the environment variable ``export CUDA_LAUNCH_BLOCKING=1`` to know exactly which CUDA kernel is causing the trouble.
- Set the environment variable ``export NCCL_DEBUG=TRACE`` to turn on more logging for NCCL.
- Set the environment variable ``export VLLM_TRACE_FUNCTION=1`` . All the function calls in vLLM will be recorded. Inspect these log files, and tell which function crashes or hangs. **Note: it will generate a lot of logs and slow down the system. Only use it for debugging purposes.**
- Set the environment variable ``export VLLM_TRACE_FUNCTION=1``. All the function calls in vLLM will be recorded. Inspect these log files, and tell which function crashes or hangs.
.. warning::
vLLM function tracing will generate a lot of logs and slow down the system. Only use it for debugging purposes.
With more logging, hopefully you can find the root cause of the issue.
Here are some common issues that can cause hangs:
- The network setup is incorrect. The vLLM instance cannot get the correct IP address. You can find the log such as ``DEBUG 06-10 21:32:17 parallel_state.py:88] world_size=8 rank=0 local_rank=0 distributed_init_method=tcp://xxx.xxx.xxx.xxx:54641 backend=nccl``. The IP address should be the correct one. If not, override the IP address by setting the environment variable ``export VLLM_HOST_IP=your_ip_address``.
- Hardware/driver setup is incorrect. GPU communication cannot be established. You can run a sanity check script below to see if the GPU communication is working correctly.
- **Incorrect network setup**: The vLLM instance cannot get the correct IP address. You can find the log such as ``DEBUG 06-10 21:32:17 parallel_state.py:88] world_size=8 rank=0 local_rank=0 distributed_init_method=tcp://xxx.xxx.xxx.xxx:54641 backend=nccl``. The IP address should be the correct one. If not, override the IP address by setting the environment variable ``export VLLM_HOST_IP=your_ip_address``.
- **Incorrect hardware/driver**: GPU communication cannot be established. You can run the following sanity check script to see if the GPU communication is working correctly.
.. code-block:: python
# save it as `test.py`` , and run it with `NCCL_DEBUG=TRACE torchrun --nproc-per-node=8 test.py`
# save it as `test.py` , and run it with `NCCL_DEBUG=TRACE torchrun --nproc-per-node=8 test.py`
# adjust `--nproc-per-node` to the number of GPUs you want to use.
import torch
import torch.distributed as dist
...
...
@@ -39,4 +42,4 @@ Here are some common issues that can cause hangs:
value = data.mean().item()
assert value == dist.get_world_size()
If the problem persists, feel free to open an `issue <https://github.com/vllm-project/vllm/issues/new/choose>`_ on GitHub, with a detailed description of the issue, your environment, and the logs.
If the problem persists, feel free to `open an issue on GitHub <https://github.com/vllm-project/vllm/issues/new/choose>`_, with a detailed description of the issue, your environment, and the logs.
@@ -20,9 +20,9 @@ The following :ref:`engine arguments <engine_args>` are specific to VLMs:
Currently, the support for vision language models on vLLM has the following limitations:
* Only single image input is supported per text prompt.
* Dynamic ``image_input_shape`` is not supported: the input image will be resized to the static ``image_input_shape``. This means model output might not exactly match the HuggingFace implementation.
* Dynamic ``image_input_shape`` is not supported: the input image will be resized to the static ``image_input_shape``. This means our LLaVA-NeXT output may not exactly match the huggingface implementation.
We are continuously improving user & developer experience for VLMs. Please raise an issue on GitHub if you have any feedback or feature requests.
We are continuously improving user & developer experience for VLMs. Please `open an issue on GitHub <https://github.com/vllm-project/vllm/issues/new/choose>`_ if you have any feedback or feature requests.