On Sat, Jan 30, 2016 at 12:53:09PM -0500, Rik van Riel wrote: > >> + delta = cputime_to_nsecs(dtime); > > > > You might want to add a comment specifying why we don't call > > cputime_to_usecs() > > directly (because we optimize if delta < TICK_NSEC). > > > > Although this has a good impact on nohz_full, it might have a tiny bad one > > on !nohz_full > > because now we first convert jiffies to nsecs (which implies a > > multiplication by 1000) > > that we later divide again by 1000. Now this is ok because I plan to > > convert tsk->utime/stime > > to nsecs and thus remove most of the cputime_t use and conversions > > everywhere. > > Isn't cputime_t in nanoseconds even on !nohz_full systems nowadays, > due to sched_clock?
Don't think so, we still use jiffy accounting for !NOHZ_FULL. > Also, a multiplication is essentially instantaneous compared to > a division, which is why Peter suggested going this way around. Yep.
