Reduce memory footprint for allreduce8 and allgather6#644
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Binyang2014 merged 2 commits intomainfrom Oct 3, 2025
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Pull Request Overview
This PR aims to reduce memory footprint for allreduce8 and allgather6 algorithms by optimizing semaphore allocation patterns. The changes move from creating new semaphores for each operation to reusing pre-allocated semaphores.
- Separates input and output semaphores in Allreduce8 to avoid unnecessary allocations
- Caches memory semaphores in AllgatherAlgo6 to prevent repeated allocations
- Removes error checking for library loading in ncclGroupStart to simplify the flow
Reviewed Changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| apps/nccl/src/nccl.cu | Simplifies ncclGroupStart by removing library load error checking |
| apps/nccl/src/allreduce.hpp | Splits deviceSemaphores into separate input/output semaphore vectors |
| apps/nccl/src/allreduce.cu | Updates semaphore usage to use separate input/output semaphores and reuse output semaphores |
| apps/nccl/src/allgather.hpp | Adds cached memory semaphores and constant for channels per connection |
| apps/nccl/src/allgather.cu | Implements semaphore caching to avoid repeated allocations |
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Reduce memory footprint for allreduce8 and allgather6
Remove libLoadSucceed check for group start