[DGD] Weird time deltas

[Raymond Jennings]

Of note, the delay actually specified in the call_out() is 0.05
exactly, with a reciprocal of 20.

On Mon, Dec 4, 2017 at 12:32 AM, Raymond Jennings <shentino at gmail.com> wrote:
> I've got a tight thread running.
>
> Every 1/20th or so of a second, it uses the kernel library's wiztool
> to generate a status report, including resources and the status
> command.
>
> As a minor performance metric to track lag, I also keep track of the
> exact time elapsed since the previous cycle was started, basically
> motivated to see how "late" the report callout fired.
>
> Oddly, instead of a buttery-smooth interval where the elapsed time is
> reported pretty close to the requested delay, I'm getting mega
> seriously weird millitime deltas that often appear to end in 5's, and
> the digits look suspiciously like multiples of a negative power of
> two.
>
> I run gentoo linux on kernel 4.14, is this some sort of artifact of
> the kernel or am I running some funky timer hardware or what?
>
> I noticed that all the actually reported deltas have reciprocals of
> 16, 32, or 21.333333333