alt Hacker Newsgood old buffer packet size
anyone old enough from dialup modems and RS232 to remember the trick of replacing the 16450 UART with 16550 if you were lucky enough to have it on a socket instead of soldered?
that took it from a 1-byte buffer to 16-bytes, instant speed boost
same idea going from X-modem to Y-modem for transfers, 128bytes vs 1024bytes before checksum
surprised ethernet by now doesn't constantly try to negotiate larger buffer windows
A lot of these drivers were written in a different era and the defaults are less appropriate now.
Having too few receive buffers leaves a trail in diagnostics (if you know to look for it!), having too many gives more subtle problems. But with 10G ethernet, you can get a lot of packets really quickly and the buffer default was probably set for a card doing 100M or 1G and the driver was updated to handle 10G without new defaults. Interrupt modulation is also common now, which is great for throughput, but means packets buffers will get more full.
I feel like segmentation offload is a nice idea, but weirdness always lurks in the shadows and I don't hesitate to turn it off if any weirdness appears. I haven't noticed a perf difference when I turn it off, but I also haven't run great tests.