[Doc] Add a perf tune section (#5127)

### What this PR does / why we need it?
This patch purpose to 
1. add a  section on os point of perf tune doc
2. Set some default env in the image for performance

- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: wangli <wangli858794774@gmail.com>

Dockerfile.a3.openEuler

@@ -21,7 +21,9 @@ ARG PIP_INDEX_URL="https://mirrors.tuna.tsinghua.edu.cn/pypi/web/simple"
 ARG MOONCAKE_TAG="v0.3.7.post2"
 ARG SOC_VERSION="ascend910_9391"
 
-ENV SOC_VERSION=$SOC_VERSION
+ENV SOC_VERSION=$SOC_VERSION \
+    TASK_QUEUE_ENABLE=1 \
+    OMP_NUM_THREADS=1
 
 RUN pip config set global.index-url ${PIP_INDEX_URL}
 
@@ -32,7 +34,7 @@ COPY . /vllm-workspace/vllm-ascend/
 SHELL ["/bin/bash", "-c"]
 
 RUN yum update -y && \
-    yum install -y git vim wget net-tools gcc gcc-c++ make cmake numactl-devel && \
+    yum install -y git vim wget net-tools gcc gcc-c++ make cmake numactl-devel jemalloc && \
     git clone --depth 1 --branch ${MOONCAKE_TAG} https://github.com/kvcache-ai/Mooncake /vllm-workspace/Mooncake && \
     cp /vllm-workspace/vllm-ascend/tools/mooncake_installer.sh /vllm-workspace/Mooncake/ && \
     ARCH=$(uname -m) && \
@@ -68,4 +70,6 @@ RUN export PIP_EXTRA_INDEX_URL=https://mirrors.huaweicloud.com/ascend/repos/pypi
 RUN python3 -m pip install modelscope 'ray>=2.47.1,<=2.48.0' 'protobuf>3.20.0' && \
     python3 -m pip cache purge
 
+RUN echo "export LD_PRELOAD=/usr/lib64/libjemalloc.so.2:$LD_PRELOAD" >> ~/.bashrc
+
 CMD ["/bin/bash"]