Is your feature request related to a problem? Please describe.
The AsyncWriteExt trait provides the write_all_buf function to write the entire contents of a Buf type to the underlying writer. However, if the buf is fragmented (eg a VecDeque or Chain), then it can have potentially bad performance with the current implementation, writing many small buffers at a time. This is because the current impl only uses chunk() to get the first chunk slice only.
If the underlying writer is_write_vectored(), write_all_buf could make use of Buf::chunks_vectored to fill an IO slice to use with poll_write_vectored.
The vectored io-slice can use a fixed size array, eg 4 or 8. When advancing the io-slice, should a chunk be removed, it could call chunks_vectored again to fill the io-slice, considering that chunks_vectored should be a fairly cheap operation.
Describe alternatives you've considered
Similar implementation discussions have occurred in #3679.
Performance testing is needed, and real-world use cases of write_all_buf should be examined
Darksonn
commented
1 month ago
Is your feature request related to a problem? Please describe.
The or Chain), then it can have potentially bad performance with the current implementation, writing many small buffers at a time. This is because the current impl only uses
AsyncWriteExttrait provides thewrite_all_buffunction to write the entire contents of aBuftype to the underlying writer. However, if the buf is fragmented (eg a VecDequechunk()to get the first chunk slice only.https://github.com/tokio-rs/tokio/blob/a02407171a3f1aeb86e7406bcac9dfb415278308/tokio/src/io/util/write_all_buf.rs#L47
Describe the solution you'd like
If the underlying writer
is_write_vectored(),write_all_bufcould make use ofBuf::chunks_vectoredto fill an IO slice to use withpoll_write_vectored.The vectored io-slice can use a fixed size array, eg 4 or 8. When advancing the io-slice, should a chunk be removed, it could call
chunks_vectoredagain to fill the io-slice, considering that chunks_vectored should be a fairly cheap operation.Describe alternatives you've considered
Similar implementation discussions have occurred in #3679. Performance testing is needed, and real-world use cases of
write_all_bufshould be examined