Llama4 Usage

Llama 4 is Meta's latest generation of open-source LLM model with industry-leading performance.

SGLang has supported Llama 4 Scout (109B) and Llama 4 Maverick (400B) since v0.4.5.

Ongoing optimizations are tracked in the Roadmap.

Launch Llama 4 with SGLang

To serve Llama 4 models on 8xH100/H200 GPUs:

python3 -m sglang.launch_server \
  --model-path meta-llama/Llama-4-Scout-17B-16E-Instruct \
  --tp 8 \
  --context-length 1000000

Configuration Tips

• OOM Mitigation: Adjust --context-length to avoid a GPU out-of-memory issue. For the Scout model, we recommend setting this value up to 1M on 8*H100 and up to 2.5M on 8*H200. For the Maverick model, we don't need to set context length on 8*H200. When hybrid kv cache is enabled, --context-length can be set up to 5M on 8*H100 and up to 10M on 8*H200 for the Scout model.

• Attention Backend Auto-Selection: SGLang automatically selects the optimal attention backend for Llama 4 based on your hardware. You typically don't need to specify --attention-backend manually:

  • Blackwell GPUs (B200/GB200): trtllm_mha
  • Hopper GPUs (H100/H200): fa3
  • AMD GPUs: aiter
  • Intel XPU: intel_xpu
  • Other platforms: triton (fallback)

  To override the auto-selection, explicitly specify --attention-backend with one of the supported backends: fa3, aiter, triton, trtllm_mha, or intel_xpu.

• Chat Template: Add --chat-template llama-4 for chat completion tasks.

• Enable Multi-Modal: Add --enable-multimodal for multi-modal capabilities.

• Enable Hybrid-KVCache: Set --swa-full-tokens-ratio to adjust the ratio of SWA layer (for Llama4, it's local attention layer) KV tokens / full layer KV tokens. (default: 0.8, range: 0-1)

EAGLE Speculative Decoding

Description: SGLang has supported Llama 4 Maverick (400B) with EAGLE speculative decoding.

Usage: Add arguments --speculative-draft-model-path, --speculative-algorithm, --speculative-num-steps, --speculative-eagle-topk and --speculative-num-draft-tokens to enable this feature. For example:

python3 -m sglang.launch_server \
  --model-path meta-llama/Llama-4-Maverick-17B-128E-Instruct \
  --speculative-algorithm EAGLE3 \
  --speculative-draft-model-path nvidia/Llama-4-Maverick-17B-128E-Eagle3 \
  --speculative-num-steps 3 \
  --speculative-eagle-topk 1 \
  --speculative-num-draft-tokens 4 \
  --trust-remote-code \
  --tp 8 \
  --context-length 1000000

• Note The Llama 4 draft model nvidia/Llama-4-Maverick-17B-128E-Eagle3 can only recognize conversations in chat mode.

Benchmarking Results

Accuracy Test with lm_eval

The accuracy on SGLang for both Llama4 Scout and Llama4 Maverick can match the official benchmark numbers.

Benchmark results on MMLU Pro dataset with 8*H100:

Commands:

# Llama-4-Scout-17B-16E-Instruct model
python -m sglang.launch_server \
  --model-path meta-llama/Llama-4-Scout-17B-16E-Instruct \
  --port 30000 \
  --tp 8 \
  --mem-fraction-static 0.8 \
  --context-length 65536
lm_eval --model local-chat-completions --model_args model=meta-llama/Llama-4-Scout-17B-16E-Instruct,base_url=http://localhost:30000/v1/chat/completions,num_concurrent=128,timeout=999999,max_gen_toks=2048 --tasks mmlu_pro --batch_size 128 --apply_chat_template --num_fewshot 0

# Llama-4-Maverick-17B-128E-Instruct
python -m sglang.launch_server \
  --model-path meta-llama/Llama-4-Maverick-17B-128E-Instruct \
  --port 30000 \
  --tp 8 \
  --mem-fraction-static 0.8 \
  --context-length 65536
lm_eval --model local-chat-completions --model_args model=meta-llama/Llama-4-Maverick-17B-128E-Instruct,base_url=http://localhost:30000/v1/chat/completions,num_concurrent=128,timeout=999999,max_gen_toks=2048 --tasks mmlu_pro --batch_size 128 --apply_chat_template --num_fewshot 0

Details can be seen in this PR.