SO_TIMESTAMP may go away

[Daniel Franke]

On Sun, Mar 3, 2019 at 9:44 PM Eric S. Raymond <esr at thyrsus.com> wrote:
>     (Also, it turns out not to be important at post-Y2K machine speeds to
>     get those arrival timestamps from the UDP layer ASAP, rather than
>     looking at packet read time in userspace. The cost of the latter,
>     naive approach is additional jitter dominated by process-scheduling
>     time; this used to be significant relative to users' accuracy
>     expectations for NTP, but scheduler timeslices have since decreased
>     by orders of magnitude and squashed the issue. We know this from some
>     tests setup having run for six months with packet-timestamp fetching
>     accidentally disabled...  But they weren't busy systems.)

Scheduler timeslices haven't changed much. The current default on
Linux is 1ms and it's been that way for a long time. What's changed is
that everybody has multicore processors now, so contention almost
never happens.