UDP Receive Buffer Size

As of quic-go v0.19.x, you might see warnings about the receive buffer size.

Experiments have shown that QUIC transfers on high-bandwidth connections can be limited by the size of the UDP receive buffer. This buffer holds packets that have been received by the kernel, but not yet read by the application (quic-go in this case). Once this buffer fills up, the kernel will drop any new incoming packet.

Therefore, quic-go tries to increase the buffer size. The way to do this is an OS-specific, and we currently have an implementation for linux, windows and darwin. However, an application is only allowed to do increase the buffer size up to a maximum value set in the kernel. Unfortunately, on Linux this value is rather small, too small for high-bandwidth QUIC transfers.

non-BSD

It is recommended to increase the maximum buffer size by running:

sysctl -w net.core.rmem_max=2500000

This command would increase the maximum receive buffer size to roughly 2.5 MB.

BSD

Taken from: https://medium.com/@CameronSparr/increase-os-udp-buffers-to-improve-performance-51d167bb1360

On BSD/Darwin systems you need to add about a 15% padding to the kernel limit socket buffer. Meaning if you want a 25MB buffer (8388608 bytes) you need to set the kernel limit to 26214400*1.15 = 30146560. This is not documented anywhere but happens in the kernel here.

To update the value immediately to 2.5M, type the following commands as root:

sysctl -w kern.ipc.maxsockbuf=3014656

Add the following lines to the /etc/sysctl.conf file to keep this setting across reboots:

kern.ipc.maxsockbuf=3014656