Messages in this thread | | | Subject | Re: [PATCH V2] sched: Improve load balancing in the presence of idle CPUs | From | Jason Low <> | Date | Thu, 26 Mar 2015 22:07:21 -0700 |
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On Fri, 2015-03-27 at 10:12 +0800, Wanpeng Li wrote: > Hi Preeti, > On Thu, Mar 26, 2015 at 06:32:44PM +0530, Preeti U Murthy wrote: > > > >1. An ILB CPU was chosen from the first numa domain to trigger nohz idle > >load balancing [Given the experiment, upto 6 CPUs per core could be > >potentially idle in this domain.] > > > >2. However the ILB CPU would call load_balance() on itself before > >initiating nohz idle load balancing. > > > >3. Given cores are SMT8, the ILB CPU had enough opportunities to pull > >tasks from its sibling cores to even out load. > > > >4. Now that the ILB CPU was no longer idle, it would abort nohz idle > >load balancing > > I don't see abort nohz idle load balancing when ILB CPU was no longer idle > in nohz_idle_balance(), could you explain more in details?
Hi Wanpeng,
In nohz_idle_balance(), there is a check for need_resched() so if the cpu has something to run, it should exit nohz_idle_balance(), which may cause it to not do the idle balancing on the other CPUs.
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