On Thu, 2017-03-30 at 00:54 +0200, Frederic Weisbecker wrote: > (Adding Thomas in Cc) > > On Wed, Mar 29, 2017 at 04:08:45PM -0400, Rik van Riel wrote: > > > > Frederic, can you think of any reason why > > the tick on nohz_full CPUs would end up aligned > > with the tick on cpu0, instead of running at some > > random offset? > > tick_init_jiffy_update() takes that decision to align all ticks. > > I'm not sure why.
I don't see why that would matter, either. > I'm not sure that randomizing the tick start per CPU would be a > right solution. Somewhere in the world you can be sure the tick > randomization of some nohz_full CPU will coincide with the tick > of CPU 0 :o) > > Or we could force that tick on nohz_full CPUs to be far from > CPU 0's tick... I'm not sure such a solution would be accepted > though. I am not sure we would have to force things. Simply getting rid of tick_init_jiffy_update and scheduling the next tick for "now + tick period" might have the same effect, when the tick gets stopped and restarted on nohz_full CPUs.