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SubjectRe: [PATCH v2 2/2] nohz: make nohz_full imply isolcpus
On 04/08/2015 05:41 AM, Peter Zijlstra wrote:
> On Mon, Apr 06, 2015 at 02:16:45PM -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.
> So the Changelog and the patch don't seem to agree with one another.
>
> The Changelog states that nohz_full should depend on isolcpus.

The git commit message says "make nohz_full imply isolcpus".
That's consistent with the code.

> The patch implies nohz_full for isolcpus.
>
> These are not the same; and I don't see the argument for the former make
> sense for the latter.
>
> In specific isolcpus without nohz_full does make sense.
>
>> Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
>> Acked-by: Mike Galbraith <umgwanakikbuti@gmail.com> ["thumbs up!"]
>> Acked-by: Rik van Riel <riel@redhat.com>
>> ---
>> 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();

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



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