[Apple Silicon] [MLX] MLX decode partial overlap scheduling for generation (async eval) (#22416)

Co-authored-by: R0CKSTAR <yeahdongcn@gmail.com>
Co-authored-by: Alex Nails <alex.nails@radixark.ai>

docs/platforms/apple_metal.md

@@ -1,6 +1,6 @@
-# Apple Silicon with Metal
+# Apple Silicon with Metal (MLX)
 
-This document describes how run SGLang on Apple Silicon using [Metal](https://developer.apple.com/metal/). If you encounter issues or have questions, please [open an issue](https://github.com/sgl-project/sglang/issues).
+This document describes how run SGLang on Apple Silicon using [Metal (MLX)](https://opensource.apple.com/projects/mlx/). If you encounter issues or have questions, please [open an issue](https://github.com/sgl-project/sglang/issues).
 
 ## Install SGLang
 
@@ -18,3 +18,57 @@ pip install --upgrade pip
 rm -f python/pyproject.toml && mv python/pyproject_other.toml python/pyproject.toml
 uv pip install -e "python[all_mps]"
 ```
+
+## Launch of the Serving Engine
+
+Launch the server with:
+
+```bash
+SGLANG_USE_MLX=1 python -m sglang.launch_server \
+  --model <MODEL_ID_OR_PATH> \
+  --disable-cuda-graph \
+  --host 0.0.0.0
+```
+
+**Key Parameters Explained:**
+
+1. `SGLANG_USE_MLX=1` - Enables the use of MLX as the SGLang runtime backend (if disabled, SGLang will fall back to `torch.mps`, which has less support)
+2. `--disable-cuda-graph` - Disables usage of CUDA graph, which is not relevant for Apple Metal.
+3. `--disable-overlap-schedule` - Disables overlap scheduling (enabled/not present by default) achieved using MLX's `async_eval()`
+
+
+## Benchmarking with Requests
+
+`sglang.benchmark_one_batch` calls the synchronous prefill/decode methods directly without going through the scheduler and the overlap code path.
+
+`sglang.benchmark_offline_throughput` can toggle overlap scheduling as it uses the scheduler and the overlap code path by using the flag `--disable-overlap-schedule`.
+
+### Throughput Testing
+
+Basic synchronous one batch throughput:
+```bash
+SGLANG_USE_MLX=1 python -m sglang.bench_one_batch \
+  --model-path <MODEL_ID_OR_PATH> \
+  --disable-cuda-graph \
+  --tp-size 1 \
+  --batch-size 1 \
+  --input-len 60 \
+  --output-len 10
+```
+
+Synchronous offline throughput:
+```bash
+SGLANG_USE_MLX=1 python -m sglang.bench_offline_throughput \
+  --model-path <MODEL_ID_OR_PATH> \
+  --disable-cuda-graph \
+  --num-prompts 1 \
+  --disable-overlap-schedule
+```
+
+Asynchronous offline throughput:
+```bash
+SGLANG_USE_MLX=1 python -m sglang.bench_offline_throughput \
+  --model-path <MODEL_ID_OR_PATH> \
+  --disable-cuda-graph \
+  --num-prompts 1
+```