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Vectored IO for write_all_buf #6575

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conradludgate opened this issue May 21, 2024 · 1 comment · Fixed by #6724
Closed

Vectored IO for write_all_buf #6575

conradludgate opened this issue May 21, 2024 · 1 comment · Fixed by #6724
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A-tokio Area: The main tokio crate C-feature-request Category: A feature request. M-io Module: tokio/io

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@conradludgate
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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.

let n = ready!(Pin::new(&mut *me.writer).poll_write(cx, me.buf.chunk())?);

Describe the solution you'd like

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

@conradludgate conradludgate added A-tokio Area: The main tokio crate C-feature-request Category: A feature request. labels May 21, 2024
@mox692 mox692 added the M-io Module: tokio/io label May 21, 2024
@Darksonn
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This seems reasonable to me.

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Labels
A-tokio Area: The main tokio crate C-feature-request Category: A feature request. M-io Module: tokio/io
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3 participants