2013/1/2 Christoph Lameter <c...@linux.com>:
> On Sat, 29 Dec 2012, Frederic Weisbecker wrote:
>
>> @@ -163,6 +164,8 @@ static int __init tick_nohz_full_setup(char *str)
>> return 1;
>> }
>> __setup("full_nohz=", tick_nohz_full_setup);
>> +#else
>> +#define have_full_nohz_mask (0)
>> #endif
>>
>> /*
>> @@ -512,6 +515,10 @@ static bool can_stop_idle_tick(int cpu, struct
>> tick_sched *ts)
>> return false;
>> }
>>
>> + /* If there are full nohz CPUs around, we need to keep the timekeeping
>> duty */
>> + if (have_full_nohz_mask && tick_do_timer_cpu == cpu)
>> + return false;
>> +
>> return true;
>> }
>>
>>
>
> Ok so I guess this means that if I setup all cpus as nohz then a random
> one will continue to do timekeeping?
In fact, although the code doesn't check that yet, you're supposed to
have at least one online CPU outside the full_nohz mask to handle
that.
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