add --blocksize to doc and script (#12187)

docker/llm/serving/xpu/docker/start-vllm-service.sh

@@ -19,6 +19,7 @@ python -m ipex_llm.vllm.xpu.entrypoints.openai.api_server \
   --port 8000 \
   --model $model \
   --trust-remote-code \
+  --block-size 8 \
   --gpu-memory-utilization 0.9 \
   --device xpu \
   --dtype float16 \

docs/mddocs/DockerGuides/vllm_docker_quickstart.md

@@ -103,6 +103,7 @@ Before performing benchmark or starting the service, you can refer to this [sect
 |`--max-model-len`| Model context length. If unspecified, will be automatically derived from the model config.|
 |`--max-num-batched-token`| Maximum number of batched tokens per iteration.|
 |`--max-num-seq`| Maximum number of sequences per iteration. Default: 256|
+|`--block-size`| vLLM block size. Set to 8 to achieve a performance boost.|
 
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