gh-120754: Update estimated_size in C truncate - #121357
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Sometimes a large file is truncated (test_largefile). While estimated_size is used as a estimate (the read will stil get the number of bytes in the file), that it is much larger than the actual size of data can result in a significant over allocation and sometimes lead to a MemoryError / running out of memory. This brings the C implementation to match the Python _pyio implementation.
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Validated memory usage decrease by running under https://www.gnu.org/software/time/ /usr/bin/time -v ./python -bb -E -Wd -m test -r -w -uall test_largefile -vvv Maximum resident set size (kbytes): 2464692 (main) -> 24532 (this pr) |
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LGTM
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vstinner
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Sometimes a large file is truncated (test_largefile). While estimated_size is used as a estimate (the read will stil get the number of bytes in the file), that it is much larger than the actual size of data can result in a significant over allocation and sometimes lead to a MemoryError / running out of memory. This brings the C implementation to match the Python _pyio implementation.
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Sometimes a large file is truncated (test_largefile). While estimated_size is used as a estimate (the read will stil get the number of bytes in the file), that it is much larger than the actual size of data can result in a significant over allocation and sometimes lead to a MemoryError / running out of memory. This brings the C implementation to match the Python _pyio implementation.
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goal: Fix buildbot failure https://github.com/python/cpython/pull/120755
Sometimes a large file is truncated (test_largefile). While estimated_size is used as a estimate (the read will get all the bytes in the file when it is wrong), that it is much larger than the actual size of data can result in a significant over allocation and sometimes lead to a MemoryError / running out of memory.
This brings the C implementation to match the Python _pyio implementation.
cc: @vstinner
I've been unable to reproduce the failure locally so far by running ./build/python -bb -E -Wd -m test -r -w -uall test_largefile. My suspicion is that the AMD64 box has limited memory. Working to try and test peak memory usage in the test / if that went down