Updated logic for extracting data sizes, made all methods static #4
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sanketpurandare
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…ytorch#139659) ### Motivation Today, watchdog only reports that it found a collective timeout: ``` [rank1]:[E1104 14:02:18.767594328 ProcessGroupNCCL.cpp:688] [Rank 1] Watchdog caught collective operation timeout: WorkNCCL(SeqNum=1, OpType=ALLREDUCE, NumelIn=200, NumelOut=200, Timeout(ms)=5000) ran for 5096 milliseconds before timing out. ``` While this is nice, it is hard to associate the error with user's program or library stack. ### This PR This PR gives watchdog the ability to report the call-time stack of the collective, so that it would be easier to track the error back to the program's behavior. The call-time stack was recorded by Flight Recorder with minimal overhead (for details, please read this [doc](https://dev-discuss.pytorch.org/t/fast-combined-c-python-torchscript-inductor-tracebacks/1158) written by @zdevito ). In `ProcessGroupNCCL`, we are only tracking / reporting the python part so that it fits most PyTorch users. ### Demo [stack_demo.py](https://gist.github.com/kwen2501/6758e18d305d67fc6f3f926217825c09). ``` TORCH_NCCL_TRACE_BUFFER_SIZE=100 torchrun --nproc-per-node 2 stack_demo.py ``` `TORCH_NCCL_TRACE_BUFFER_SIZE` is for turning on the Flight Recorder. Output: ``` [rank0]:[E1104 14:19:27.591610653 ProcessGroupNCCL.cpp:695] Stack trace of the timedout collective operation: #0 all_reduce from /data/users/kw2501/pytorch/torch/distributed/distributed_c10d.py:2696 #1 wrapper from /data/users/kw2501/pytorch/torch/distributed/c10d_logger.py:83 #2 bar from /data/users/kw2501/sync_async/repro.py:15 #3 foo from /data/users/kw2501/sync_async/repro.py:24 #4 main from /data/users/kw2501/sync_async/repro.py:34 pytorch#5 <module> from /data/users/kw2501/sync_async/repro.py:40 [rank1]:[E1104 14:19:27.771430164 ProcessGroupNCCL.cpp:695] Stack trace of the timedout collective operation: #0 all_gather_into_tensor from /data/users/kw2501/pytorch/torch/distributed/distributed_c10d.py:3630 #1 wrapper from /data/users/kw2501/pytorch/torch/distributed/c10d_logger.py:83 #2 baz from /data/users/kw2501/sync_async/repro.py:20 #3 foo from /data/users/kw2501/sync_async/repro.py:26 #4 main from /data/users/kw2501/sync_async/repro.py:34 pytorch#5 <module> from /data/users/kw2501/sync_async/repro.py:40 ``` From the log above, we can tell that `bar()` and `baz()` are the places where the two ranks divert. Pull Request resolved: pytorch#139659 Approved by: https://github.com/wconstab, https://github.com/fduwjj
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