Okay, so this is going to cross some borders about where the issue might be... I'm not sure where the issue is, but hopefully someone might at least have a thought.

I long ago started writing an AFP client stack in Perl. Yes, I did that. The question isn't if that's possible. (If you're interested in seeing it, it's [https://github.com/demonfoo/afp-perl](here).)

When trying to run the code on UN*X platforms (Linux, macOS, *BSD, Solaris/OpenIndiana), it works well. I've even added sendfile() support for uploading, for the platforms that support it. Over my home network, from my Linux machine to my TrueNAS Core NAS, I can transfer data over 10GbE at 5-6 Gbps. So I like to think it's pretty efficient... but Windows is a whole other world of pain.

I've recently been optimizing it, and Devel::NYTProf has been very helpful. I'd tried running it on Windows in the past, and running into issues. I originally thought it might be an issue with Perl threads (yes, it's using those too...), but based on profiling, it's not. It sends a command packet, which is just 36 bytes long, which apparently Windows' TCP stack doesn't much appreciate. It sits there for a really long time waiting for the command data to send while uploading, and I'm not sure why; using Sys::Sendfile, which wraps the Win32 TransmitFile() function, takes 5x less time for some reason, even though each call to it sends 512 KiB. And yes, I am disabling Nagle's algorithm, and setsockopt() seems to indicate it worked.

Thoughts on what I'm doing wrong?

submitted by /u/demonfoo
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