Use PyBytes as backing for Buffer #1817
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Summary: This sets us up for the next diff by creating `FragmentedPart` Currently our pickle is still not truly zero copy because the Pickler calls `Buffer::write()` which is copying bytes from `PyBytes` to `BytesMut` via `extend_from_slice()`. This is especially problematic for large messages (100KB+) as we are spending a lot of CPU cycles handling page faults. For a 1MB message pickling can take as long as 600us To avoid copies, we can just make `Buffer` backed by a `Vec<PyBytes>` with each call to `Buffer::write()` pushing the PyBytes to the Vec. As a result of this, the PyBytes are physically fragmented despite being logically contiguous. To make this work, we will have a NewType with called `FragmentedPart` with a `::Fragmented` variant wrapping `Vec<Part>` and a `::Contiguous` variant wrapping `Part`. Similar to `Part`, `FragmentedPart` also just collects during serialization. When we receive the frame on the other end of the wire, we reconstruct it contiguously in the `FragmentedPart::Contiguous` variant so that we can easily consume it to create a single contiguous `bytes::Bytes` Differential Revision: D86696390
Summary:
Currently our pickle is still not truly zero copy because the Pickler calls `Buffer::write()` which is copying bytes from `PyBytes` to `BytesMut` via `extend_from_slice()`.
To avoid copies, we can just make `Buffer` backed by a `Vec<PyBytes>` with each call to `Buffer::write()` pushing the PyBytes to the Vec.
The following figures show a round trip produced from
```
await am.echo.call(b"x" * 1024 * 1024)
```
Before:
Send path: 600us pickle (purple), write frames (dark green), receive frames (light green), 130 us unpickle,
Reply path: 600us pickle, write frames, receive frames, 130us unpickle
{F1983399784}
After:
Send path: 20us pickle (purple), write frames (dark green), receive frames (light green), 200us unpickle,
Reply path: 20us pickle, write frames, receive frames, 150us unpickle
{F1983399596}
Differential Revision: D86696391
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Summary:
Currently our pickle is still not truly zero copy because the Pickler calls
Buffer::write()which is copying bytes fromPyBytestoBytesMutviaextend_from_slice().To avoid copies, we can just make
Bufferbacked by aVec<PyBytes>with each call toBuffer::write()pushing the PyBytes to the Vec.The following figures show a round trip produced from
Before:
Send path: 600us pickle (purple), write frames (dark green), receive frames (light green), 130 us unpickle,
Reply path: 600us pickle, write frames, receive frames, 130us unpickle
{F1983399784}
After:
Send path: 20us pickle (purple), write frames (dark green), receive frames (light green), 200us unpickle,
Reply path: 20us pickle, write frames, receive frames, 150us unpickle
{F1983399596}
Differential Revision: D86696391