On 2020/9/12 7:04, Li, Aubrey wrote:
> On 2020/9/12 0:28, Qais Yousef wrote:
>> On 09/10/20 13:42, Aubrey Li wrote:
>>> Added idle cpumask to track idle cpus in sched domain. When a CPU
>>> enters idle, its corresponding bit in the idle cpumask will be set,
>>> and when the CPU exits idle, its bit will be cleared.
>>>
>>> When a task wakes up to select an idle cpu, scanning idle cpumask
>>> has low cost than scanning all the cpus in last level cache domain,
>>> especially when the system is heavily loaded.
>>>
>>> Signed-off-by: Aubrey Li <aubrey...@linux.intel.com>
>>> ---
>>> include/linux/sched/topology.h | 13 +++++++++++++
>>> kernel/sched/fair.c | 4 +++-
>>> kernel/sched/topology.c | 2 +-
>>> 3 files changed, 17 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
>>> index fb11091129b3..43a641d26154 100644
>>> --- a/include/linux/sched/topology.h
>>> +++ b/include/linux/sched/topology.h
>>> @@ -65,8 +65,21 @@ struct sched_domain_shared {
>>> atomic_t ref;
>>> atomic_t nr_busy_cpus;
>>> int has_idle_cores;
>>> + /*
>>> + * Span of all idle CPUs in this domain.
>>> + *
>>> + * NOTE: this field is variable length. (Allocated dynamically
>>> + * by attaching extra space to the end of the structure,
>>> + * depending on how many CPUs the kernel has booted up with)
>>> + */
>>> + unsigned long idle_cpus_span[];
>>
>> Can't you use cpumask_var_t and zalloc_cpumask_var() instead?
>
> I can use the existing free code. Do we have a problem of this?
>
>>
>> The patch looks useful. Did it help you with any particular workload? It'd be
>> good to expand on that in the commit message.
>>
> Odd, that included in patch v1 0/1, did you receive it?
I found it at here:
https://lkml.org/lkml/2020/9/11/645
>
> Thanks,
> -Aubrey
>
