Fix misusing the "_is_cuda". #7091
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Summary of Changes
Hello @sogalin, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request addresses a minor bug identified in a previous PR by fixing a variable name typo. The change ensures that the alternate CUDA stream within the memory pool is correctly initialized only when the device is indeed CUDA, preventing potential issues related to device-specific operations.
Highlights
- Bug Fix: Corrected the variable name used to check for CUDA device presence when initializing the alternate stream in the
MemoryPoolconstructor.
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Code Review
This pull request correctly addresses a bug in MHATokenToKVPool initialization where alt_stream could be incorrectly initialized on non-CUDA systems. The original code, if is_cuda:, evaluated the truthiness of the is_cuda function object itself (which is always true if the function is defined), rather than calling the function to check for CUDA availability. This could lead to an AttributeError (e.g., attempting to call torch.cpu.Stream()) if CUDA was not available. The change to use if _is_cuda, which references a module-level boolean variable (_is_cuda = is_cuda()) reflecting actual CUDA availability, effectively resolves this critical issue.
To enhance long-term maintainability and prevent regressions, it would be beneficial to ensure that unit tests cover the initialization of MHATokenToKVPool in non-CUDA environments (e.g., with device="cpu" or by mocking torch.cuda.is_available to return False). Such tests would confirm that alt_stream is correctly set to None in these scenarios, safeguarding against similar issues in the future.
Motivation
Fix PR#6475
Modifications
Fix the misusing _is_cuda in the script.
Checklist