Messages in this thread | | | Subject | Re: nohz: remove nohz_cpu_mask | From | "Alex,Shi" <> | Date | Fri, 15 Jul 2011 08:51:45 +0800 |
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On Tue, 2011-07-12 at 01:30 +0800, Paul E. McKenney wrote: > On Mon, Jul 11, 2011 at 08:47:05AM +0800, Alex,Shi wrote: > > RCU didn't use this global variable now. Currently no user on it. > > Indeed. RCU's use of it turned out to be quite buggy. :-( > > > Since the ts->do_timer_last is not the real last periodic tick cpu in > > most of time. I once want to compare the cpu_online_mask and > > nohz_cpu_mask to get a real one, and than only let that cpu sleep > > shorter, other cpu will try to sleep KTIME_MAX, that need a extra lock > > for nohz_cpu_mask. But I checked my all platforms, from NHM-EX server to > > laptops, all of them are waked up a few times per second. So, the > > advantage is only in theory. > > > > Since no clear usage of this variable, why not remove it? That can save > > a cache-line in all cpus and reduce atomic sync contention. > > Works for me! > > Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> >
Thomas, would you like to give some comments of this?
Best regards! Alex
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