# Multi-LoRA Tuning

**Note**: The LoRA configuration folder should be specified by exporting `VLLM_TUNED_CONFIG_FOLDER=/path/to/configs`. Without this, the shrink/expand kernels will use default configurations.

## Tuning Process

Multi-lora shrink/expand Triton kernel tuning follows a similar methodology from [Triton MoE tuning](https://github.com/vllm-project/vllm/blob/main/benchmarks/kernels/benchmark_moe.py).

**Step 1**
Define the searching space. An example searching space:

```python
block_m_range = [16, 32, 64, 128, 256]
block_n_range = [32, 64, 128, 256]
block_k_range = [32, 64, 128, 256]
num_warps_range = [4, 8]
num_stage_range = [2, 3, 4, 5]
num_ctas_range = [1]
split_k_range = [4, 8, 16, 32, 64]
```

**Step 2**
Get all hidden_state sizes and num_slices that the target model uses for a specific TP size.

For example, we can aquire those info by simply checking [add_lora_linear](https://github.com/li2haipeng/vllm/blob/multi_lora_v01011/vllm/lora/punica_wrapper/punica_gpu.py#L192):

```python
print(f"x_shape: {x.view(-1, x.shape[-1]).shape}")
print(f"num_sclises: {len(output_slices)}")
for i in range(len(output_slices)):
    print(f"a{i} shape: {lora_a_stacked[i].shape}")
    print(f"b{i} shape: {lora_b_stacked[i].shape}")
print("y_shape", y.shape)
```

**Step 3**
Benchmark the shrink/expand kernel runtime with different kernel configurations generated from the pre-defined search space by performing a grid search to find the optimal kernel configuration. vLLM's [benchmark_lora.py](https://github.com/vllm-project/vllm/blob/main/benchmarks/kernels/benchmark_lora.py) can be used to search for configurations for different shapes.

## Config Files

### File Name

For `shrink`, the config file is named as `{gpu_name}_SHRINK.json`, e.g. `NVIDIA_H200_SHRINK.json`.

For `expand`, the config fileis named as `{gpu_name}_EXPAND_{add_input}.json`, e.g. `NVIDIA_H200_EXPAND_TRUE.json`.

The `gpu_name` can be automatically detected by calling `torch.cuda.get_device_name()`

### Json Structure

Optimal kernel configuration files are saved as JSON files with the structure `config_data[max_loras][num_slices][m][k][n]`
