[Feature] Add SiMM as sglang HiCache Storage backend

[hhu-scitix]

Description

SiMM(Scitix In-Memory Middleware) is a distributed, high-performance, elastic cache acceleration layer for all AI workloads.

Feature

1. support 'page_first' and 'page_first_direct' for zero copy cache layout.
2. support numa-aware RDMA nic select.

Benchmarking and Profiling

Test DeepSeek R1 on 8* H200 141G with 8*400Gbps RoCE network (MT4129).

GPU Driver: 570.86.15, CUDA version: 12.9

Use benchmark/hicache/bench_multiture.py.

client:

python3 bench_multiturn.py \
  --num-clients 128 --max-parallel * \
  --request-length 8000 --output-length 200 \
  --host 127.0.0.1 --port 8080 --disable-auto-run \
  --disable-random-sample \
  --model-path /models/preset/deepseek-ai/DeepSeek-R1/v1.0 \
  --num-rounds=* --seed=* \
  --ready-queue-policy=fifo \
  --sub-question-input-length=128

server:

python3 -m sglang.launch_server \
  --model /models/preset/deepseek-ai/DeepSeek-R1/v1.0 \
  --trust-remote-code \
  --tp 8 --mem-fraction-static 0.75 \
  --page-size 64 \
  --enable-hierarchical-cache \
  --hicache-ratio 1.1 \
  --hicache-mem-layout page_first_direct \
  --hicache-io-backend direct \
  --hicache-storage-backend simm \
  --hicache-write-policy write_through \
  --hicache-storage-prefetch-policy timeout \
  --hicache-storage-backend-extra-config '{"manager_address":"0.0.0.0:30001"}' \
  --port 8080

rounds	parallel	Req throughput (req/s)		Input throughput (token/s)		Output throughput (token/s)		SLO (ms)
		SiMM	GPU	SiMM	GPU	SiMM	GPU	SiMM		GPU
								TTFT	E2E Latency	TTFT	E2E Latency
3	4	0.81	0.80	6856.36	6810.02	161.14	159.83	0.43	3.20	0.50	3.45
	8	0.97	0.90	8250.51	7670.94	193.62	180.09	0.47	3.84	0.56	4.05
	16	0.97	1.02	8236.79	8653.88	193.49	203.30	0.49	3.73	0.63	4.92
10	4	0.88	0.80	8153.91	7767.07	168.62	160.61	0.41	3.11	0.56	3.57
	8	0.97	0.91	9353.14	8819.79	193.55	182.40	0.43	3.65	0.66	4.51
	16	1.01	0.98	9733.29	9459.86	201.32	195.47	0.50	4.08	0.72	5.23

'GPU' means only use GPU cache (no use hicache).

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.
• Follow the SGLang code style guidance.