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SubjectRe: [PATCH 2/2] nohz: make nohz_full imply isolcpus
On 04/03/2015 01:42 PM, Frederic Weisbecker wrote:
> On Fri, Apr 03, 2015 at 12:24:08PM -0400, cmetcalf@ezchip.com wrote:
>> From: Chris Metcalf <cmetcalf@ezchip.com>
>>
>> It's not clear that nohz_full is useful without isolcpus also
>> set, since otherwise the scheduler has to run periodically to
>> try to determine whether to steal work from other cores.
>>
>> Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
> I think Rick has a similar patch.

I didn't see anything relevant in linux-next, though I did see
cpu_isolated_map
made into a public symbol in a recent commit by Rik.

Rik, what's the change you're proposing that's similar to this one? Thanks!

>> ---
>> I am puzzled why this has not been done before, so I suspect
>> there is some argument against it that I am missing, but I
>> wasn't able to turn anything up by searching LKML.
>>
>> kernel/sched/core.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index f0f831e8a345..275f12c608f2 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -6836,6 +6836,7 @@ static int init_sched_domains(const struct cpumask *cpu_map)
>> doms_cur = alloc_sched_domains(ndoms_cur);
>> if (!doms_cur)
>> doms_cur = &fallback_doms;
>> + tick_nohz_full_set_cpus(cpu_isolated_map);
>> cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
>> err = build_sched_domains(doms_cur[0], NULL);
>> register_sched_domain_sysctl();
>> --
>> 2.1.2
>>

--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com



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