[ntp:questions] Effect of Gigabit Interrupt coalescence on ntp timing

unruh unruh at invalid.ca
Tue Jun 12 20:44:04 UTC 2012

On 2012-06-12, David Malone <dwmalone at walton.maths.tcd.ie> wrote:
> unruh <unruh at invalid.ca> writes:
>>I have posted a web page
> Should the "rx-users" setting be "rx-usecs"? It would be nice if


> some of these cards actually timestamped the frames when received
> and then the timestamp provided by SO_TIMESTAMP or similar could
> be corrected. It seems only a few cards can do this though.

It would be nice. But then what clock would they use to timestamp the
packets. If it is an onboard network card clock one would then also have to
discipline that network card clock ( or at least calbrate it, and as we
know that calibration changes so it would have to be another continuous
calibration of that clock.)

> (On FreeBSD these interrupt mitigation techniques should be tweakable
> using the sysctls under the dev.em sysctl tree.)
>         David.

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