Skip coercing to bytes in merge_frames#3960
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mrocklin merged 1 commit intodask:masterfrom Jul 14, 2020
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As the frames we receive are typically mutable, non-`bytes` objects like `bytearray`s or NumPy `ndarray`s, coercing to `bytes` at this stage triggers a copy of all frames. As we are going to toss those copied versions anyways when joining them into a larger `bytes` object, this ends up being wasteful with memory. Fortunately `bytes.join(...)` accepts any and all `bytes`-like objects. So instead just pass them all through as-is to `bytes.join(...)`, which is free and doesn't require a copy. Should cutdown on the memory usage in this part of the code.
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FWIW here's a little example showing this works. In [1]: import numpy as np
In [2]: b"".join([
...: b"abc",
...: bytearray(b"def"),
...: memoryview(b"ghi"),
...: np.arange(106, 109, dtype="u1")
...: ])
Out[2]: b'abcdefghijkl'This was raised in Python issue ( https://bugs.python.org/issue15958 ) and implemented in commit ( python/cpython@cfc22b4 ) as part of Python 3.4+. |
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I kicked the CI here so test should be passing now |
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As the frames we receive are typically mutable, non-
bytesobjects likebytearrays or NumPyndarrays, coercing tobytesat this stage triggers a copy of all frames. As we are going to toss those copied versions anyways when joining them into a largerbytesobject, this ends up being wasteful with memory. Fortunatelybytes.join(...)accepts any and allbytes-like objects. So instead just pass them all through as-is tobytes.join(...), which is free and doesn't require a copy. Should cutdown on the memory usage in this part of the code.