[Benchmark] Correctly kill vllm process in performance benchamrk

[Potabk]

What this PR does / why we need it?

vLLM now names the process with VLLM prefix after vllm-project/vllm#21445, we should kill the correct process name after one iteration benchmark to avoid OOM issue

Does this PR introduce any user-facing change?

How was this patch tested?

• vLLM version: v0.10.1.1
• vLLM main: vllm-project/vllm@e599e2c

[gemini-code-assist]

Code Review

This pull request correctly adds a command to terminate vLLM processes using their new VLLM process name, which is an important fix for resource cleanup in the benchmark suite. However, I've identified a critical issue with an existing command in the same function that indiscriminately kills all python3 processes. This is a significant risk and could lead to terminating unrelated processes. My review includes a suggestion to remove this hazardous command, thereby improving the script's safety and reliability.

[gemini-code-assist]

Killing all processes named python3 is overly broad and poses a significant risk of terminating unrelated user or system processes, which could lead to data loss or system instability. This is a critical issue for script robustness.

Since vLLM processes are now specifically identified by the VLLM prefix, the generic pgrep python3 command is likely redundant and dangerous. It should be removed to make the cleanup process more targeted and safe.

Suggested change

	pgrep python3 | xargs -r kill -9
	# vLLM now names the process with VLLM prefix after https://github.com/vllm-project/vllm/pull/21445
	pgrep VLLM | xargs -r kill -9
	# vLLM now names the process with VLLM prefix after https://github.com/vllm-project/vllm/pull/21445
	pgrep VLLM | xargs -r kill -9

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