As the [epoll documentation points out](https://man7.org/linux/man-pages/man7/epoll.7.html), a read that only partially fills a buffer is sufficient to show that the socket buffer has been drained.
We can take advantage of this by clearing readiness in this case, which seems to significantly improve performance under certain conditions.
Co-authored-by: Carl Lerche <[email protected]>
This fixes#4801, where, as a result of https://github.com/rust-lang/rust/pull/95469, our implementation of cat used for this test no longer works, as stdio functions on windows now can abort the process if the pipe is set to nonblocking mode.
Unfortunately in windows, setting one end of the pipe to be nonblocking makes the whole thing nonblocking, so when, in tokio::process we set the child pipes to nonblocking mode, it causes serious problems for any rust program at the other end.
Fixing this issue is for another day, but fixing the tests is for today.
Noah Kennedy