Performance issue on Mac with M1 pro about magic-wormhole.rs HOT 3 CLOSED

Cool, those might make some numbers suitable to add to "the ecosystem doc" (https://github.com/magic-wormhole/magic-wormhole/blob/master/docs/ecosystem.rst) or somewhere in the general protocols repo

from magic-wormhole.rs.

Wonder what could be the bottleneck.

There could be many reasons why the mac implementation is slower in your specific case. It's impossible to tell, unless you profile it. Could be interesting to know. Just to make sure: You compile against aarch64, not against x86_64?

from magic-wormhole.rs.

I found the potential issue. I reviewed the code of the python and golang version with a debugger and found that the rust implementation has a different chunk size for each send. Python and Golang implementations both send 16KB at a time while the rust version sends 4KB at a time.

After setting chunk size to 16KB I get full speed.

Python

File sending starts from here https://github.com/magic-wormhole/magic-wormhole/blob/02407c4aa4cc3f8d8cd01d549fdc72a5f5d77010/src/wormhole/cli/cmd_send.py#L442

fs = basic.FileSender()

with self._timing.add("tx file"):
    with progress:
        if filesize:
            # don't send zero-length files
            yield fs.beginFileTransfer(
                self._fd_to_send,
                record_pipe,
                transform=_count_and_hash)

The chunk size is defined in twisted package twisted.protocols.basic.FileSender

File chunks are read here https://github.com/twisted/twisted/blob/02a2b658cd1ade5d7f41f97d898913686313e615/src/twisted/protocols/basic.py#L892

CHUNK_SIZE is a constant defined as CHUNK_SIZE = 2**14 (which is 16384bytes, 16kB)
at https://github.com/twisted/twisted/blob/02a2b658cd1ade5d7f41f97d898913686313e615/src/twisted/protocols/basic.py#L857

Golang

The golang implementation also defines chunk size to be 16KB (recordSize := (1 << 14))

See https://github.com/psanford/wormhole-william/blob/68dc3447a8585b060fb1e6836a23847700ab9207/wormhole/send.go#L363

Rust

Rust is using 4KB.

I changed 4096 to 16384 and build a release build that gives me 117MB/s when sender is M1 pro Mac.

I think the rust implementation can also use 16KB.

from magic-wormhole.rs.