[release v2.0.1] Revisit torch._six.string_classes removal (#97737, #97789, #97863)#98055
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atalman merged 3 commits intopytorch:release/2.0from Apr 5, 2023
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…es (pytorch#97737) Slack thread: https://pytorch.slack.com/archives/GEEQ2K4MD/p1679962409906099 I was seeing some massive (~2x) slowdowns on a job after running it on PyTorch 2.0. From some profiling in `py-spy` it looked like the pin_memory thread was doing a lot more work than before. Looking at a trace in `nsys` I saw the thread doing the forward pass having a bunch of `pthread_cond_timedwait` with GIL reacquire calls in it’s call stack, and it seemed like the thread doing the forward pass was getting blocked (waiting for the GIL) by the pin memory thread (which was holding the GIL). After some debugging I found out the issue. If a `bytes` was passed into `pin_memory`, previously in 1.13 (before pytorch#94709) it would short-circuit and return here https://github.com/pytorch/pytorch/blob/d922c29a22e4bf0fba49526f7536395eb8cd66f4/torch/utils/data/_utils/pin_memory.py#L54-L55 since `bytes` was in `torch._six.string_classes`: ``` >>> from torch._six import string_classes >>> string_classes (<class 'str'>, <class 'bytes'>) >>> ``` However after pytorch#94709, if a `bytes` was passed into `pin_memory` it would fall into here instead https://github.com/pytorch/pytorch/blob/c263bd43e8e8502d4726643bc6fd046f0130ac0e/torch/utils/data/_utils/pin_memory.py#L68-L73 because the previous check is now doing `isinstance(data, str)` instead of `isinstance(data, (str, bytes))`! https://github.com/pytorch/pytorch/blob/c263bd43e8e8502d4726643bc6fd046f0130ac0e/torch/utils/data/_utils/pin_memory.py#L56-L57 As a result, `pin_memory` gets called recursively for each element in the `bytes` leading to a ton of wasted recursion. This also explains the slowdown / GIL contention I was seeing. This PR simply changes `isinstance(data, str)` to `isinstance(data, (str, bytes))` to match the behavior before pytorch#94709 Pull Request resolved: pytorch#97737 Approved by: https://github.com/albanD, https://github.com/NivekT
Similar to pytorch#97737, a previous auto-refactor changed how `bytes` are handled during collation, which can potentially lead to performance regression. This PR undoes that. Pull Request resolved: pytorch#97789 Approved by: https://github.com/albanD
…97863) Revisit `torch._six.string_classes` (which is `(str, bytes)`) removal: `isinstance(obj, string_classes) -> isinstance(obj, str)`. Both `str` and `bytes` are `Sequence` classes. ```python In [1]: from typing import Sequence In [2]: issubclass(bytes, Sequence) Out[2]: True In [3]: issubclass(str, Sequence) Out[3]: True ``` Re-add `bytes` to type guards like: ```python def is_seq(obj): return isinstance(obj, Sequence) and not isinstance(obj, (str, bytes)) ``` Ref: - pytorch#94709 (comment) - pytorch#97737 - pytorch#97789 Pull Request resolved: pytorch#97863 Approved by: https://github.com/Skylion007, https://github.com/albanD
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🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/98055
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This was referenced Apr 5, 2023
atalman
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Apr 5, 2023
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Reland fixes #97737, #97789, #97863 to release 2.0.1
torch._six.string_classesremoval (#94709) #97863