Hi, The bump upon each statclock is: ((cur_systimer - prev_systimer) * systimer_freq) >> 32
systimer_freq can be extracted from following sysctl in userspace: sysctl kern.cputimer.freq statclock is called at stathz frequency. Thanks, sephe On Mon, Sep 19, 2016 at 12:46 AM, Stuart Nelson <[email protected]> wrote: > Hey all, > > I'm following up on some work from this old thread for monitoring CPU time: > https://www.dragonflybsd.org/mailarchive/users/2010-04/msg00056.html > > The code I have is essentially the one shown in the link, but I'm attempting > to find the actual number of seconds spent in each state. I'm doing this by > dividing each value by clockrate.stathz, e.g.: > > > user += cp_t[cpu].cp_user / clockrate.stathz; > > > Relevant code is here: > https://github.com/stuartnelson3/node_exporter/blob/2b5a581942ac31b501438d402274100df1f7d3d6/collector/cpu_dragonfly.go#L50-L98 > > My question is about the units on struct members in kinfo_cputime (the > source of cp_user et al.). The values I'm getting out seem to be growing at > a rate that indicates I'm not looking at seconds, but something smaller. > > I'm looking at the rate of change of cpu time on my personal machine running > dragonfly vs. a machine running linux. The implementation is the same: get > user time, divide by 100Hz to get the value in seconds, and find the rate of > change between two collections in fixed time window. The dragonfly rate of > change seems to be larger by about 2 orders of magnitude, which is why I'm > asking about the units. > > For reference, the dragonfly node I'm looking at is reporting ~200 increase > per second in cpu time for user and sys with loadavg ~0.1%, whereas the > linux node is reporting values <10 with loadavg ~15%. > > I'm improving dragonfly support for the node_exporter for Prometheus, a > metrics and monitoring solution that is used mostly in the linux community. > I'm assuming the linux implementation for finding cpu time in seconds is > correct, and it's also the implementation used for finding cpu seconds for > freebsd. It just struck me as unlikely that my old dell running dragonfly > would have a rate of change at a fraction of the load that was so > drastically different. > > If there is anything I can clarify don't hesitate to write back! > > Thanks, > Stuart > > -- Tomorrow Will Never Die
