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Prashant Lakhera
Prashant Lakhera

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πŸš€ Multi-GPU Inference: explained simply πŸš€

When people first hear multiple GPUs, it’s easy to think:

More GPUs = faster LLM.

But that’s not always the case.

The real question is:

Why do we need multiple GPUs in the first place?

There are mainly two problems:

πŸ“Œ The model fits on one GPU, but we need to serve more users.

πŸ“Œ The model is too large to fit on a single GPU.

And that leads us to three important techniques:

1️⃣ Data Parallelism β†’ Copy the model

Run a complete copy of the same model on multiple GPUs and distribute incoming requests among them.

Goal: Higher throughput

2️⃣ Tensor Parallelism β†’ Split the layer

Split computations inside a model layer across multiple GPUs.

Because the GPUs need to communicate frequently, high-speed GPU interconnects such as NVLink and NVSwitch become very important.

Goal: Run larger models and parallelize computation

3️⃣ Pipeline Parallelism β†’ Split the layers

Different groups of model layers run on different GPUs.

For example:

GPU 0 β†’ Layers 1–4

GPU 1 β†’ Layers 5–8

GPU 2 β†’ Layers 9–12

The output of one stage is passed to the next, almost like an assembly line.

Goal: Scale very large models across GPUs and nodes

The easiest way to remember all three:

Data Parallelism β†’ Copy the model

Tensor Parallelism β†’ Split the layer

Pipeline Parallelism β†’ Split the layers

And for very large deployments, these techniques can also be combined using Hybrid Parallelism.

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