Hi Wanpeng On 03/27/2015 07:42 AM, 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?
When the ILB CPU pulls load in rebalance_domains(), its idle state is set to CPU_NOT_IDLE. "" idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; And, When nohz_idle_balance() is called, the state of idle of ILB CPU is checked before proceeding with load balancing on idle CPUs. "" if (idle != CPU_IDLE || !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) goto end; You see that nohz idle balancing gets aborted. Regards Preeti U Murthy > > Regards, > Wanpeng Li > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/