*: use our own std::io::copy() implementation #290
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src/io.rs
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| /// This is like `std::io:copy()`, but uses a buffer larger than 8 KiB. |
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Let's say why we do that too. (It's in the commit message yes, but that stuff can get harder to find as code moves around)
I also looked at this for ostree a while ago...see ostreedev/ostree@16c31a9b5#diff-7833e28ecd7891cb43d466346f39acbdR828
And linked from there: https://github.com/coreutils/coreutils/blob/master/src/ioblksize.h
Of course both that and the coreutils one are pre-Meltdown/Spectre. And also pre-io-uring (which is going to dramatically change things like this).
Anyways seems fine as is, but it's worth thinking about e.g. whether we should argue for std to do this by default (although that'd be easier if there was a version that knew at least a lower bound for how much data we were going to be copying, which would help avoid allocating large buffers for small copies)
The std one uses an 8 KiB buffer. Use a larger buffer to amortize syscall overhead.
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Updated. There's already an upstream bug: rust-lang/rust#49921 |
The
stdone uses an 8 KiB buffer. Use a larger buffer to amortize syscall overhead.