I have completed my Armbian NTP server based on the wonderful little NanoPi Neo3. However something bothers me a bit, i.e. how much delay or latency is in eth0 (It is a 1Gbs port).
By checking the default eth0 settings (ethtool -c eth0) I have the parameters below. In particular rx-usec = 327usec means that when a packet is received, the IRQ to alert the CPU can be delayed up to 327usec. With these settings on the nanopi (NTP server) I get about 1msec delay on the NTP client (Windows PC). By cutting the rx-usecs to 35 usecs I get a delay on the client of about 450usec, so a massive improvement and 30% faster than rpi 4.
At the moment, in order to change this parameter after boot, I have the two lines below into /etc/rc.local, the delay is needed as the command may be issued before eth0 is ready to accept it (I found this the hard way):
sleep 10
sudo ethtool -C eth0 rx-usecs 35
The question: Is there a place where those eth0 defaults are saved? If there is a config file somewhere or even in the Kernel (I can re-build it) I could change them to a new default and avoid the rc.local hassle and delay. I guess I like a leaner approach :-)
vmiceli got a reaction from lanefu in Defaults for Ethernet coalesce?