[Misc] [ROCm] Prevent surplus tensor reshape

[zsolt-borbely-htec]

In case of ROCm, there is no need to reshape.

[gemini-code-assist]

Summary of Changes

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This pull request aims to optimize the attention backend for ROCm environments by eliminating an unnecessary tensor reshape operation. While the stated intent is to prevent a surplus reshape, the provided patch primarily focuses on adjusting the indentation of an existing reshape operation, likely correcting its scope or conditional execution within the codebase.

Highlights

• Performance Optimization for ROCm: The primary goal of this pull request, as stated in its title and description, is to prevent a surplus tensor reshape operation that is deemed unnecessary when running on ROCm hardware, aiming to improve efficiency and streamline tensor handling.
• Code Structure Adjustment: The actual change observed in the patch involves a minor indentation adjustment for a query.reshape operation within vllm/v1/attention/backends/triton_attn.py. Specifically, the line query = query.reshape((num_tokens, num_heads, head_size)) on line 379 was moved two spaces further inward (from 12 to 14 spaces). This appears to be a code formatting or scope correction, which, based on the PR description, might be part of a larger conditional logic that prevents the reshape for ROCm.

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[gemini-code-assist]

Code Review

This pull request correctly addresses an unnecessary tensor reshape operation in the Triton attention backend for ROCm platforms when using an fp8 key-value cache. By adjusting the indentation, the query.reshape() call is now conditionally executed only when query quantization (which is skipped on ROCm) has taken place. This ensures the query tensor maintains its correct 3D shape without a redundant reshape on ROCm, while still being correctly processed on other platforms. The change is a good optimization and improves code clarity for this specific path.

[github-actions]

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[zsolt-borbely-htec]

cc: @gshtras

[gshtras]

Good catch, thanks for the fix!