On 05/25/2018 05:40 AM, Patrick Bellasi wrote:
> On 24-May 11:22, Waiman Long wrote:
>> On 05/24/2018 11:16 AM, Juri Lelli wrote:
>>> On 24/05/18 11:09, Waiman Long wrote:
>>>> On 05/24/2018 10:36 AM, Juri Lelli wrote:
>>>>> On 17/05/18 16:55, Waiman Long wrote:
>>>>>
>>>>> [...]
>>>>>
>>>>>> + A parent cgroup cannot distribute all its CPUs to child
>>>>>> + scheduling domain cgroups unless its load balancing flag is
>>>>>> + turned off.
>>>>>> +
>>>>>> + cpuset.sched.load_balance
>>>>>> + A read-write single value file which exists on non-root
>>>>>> + cpuset-enabled cgroups. It is a binary value flag that accepts
>>>>>> + either "0" (off) or a non-zero value (on). This flag is set
>>>>>> + by the parent and is not delegatable.
>>>>>> +
>>>>>> + When it is on, tasks within this cpuset will be load-balanced
>>>>>> + by the kernel scheduler. Tasks will be moved from CPUs with
>>>>>> + high load to other CPUs within the same cpuset with less load
>>>>>> + periodically.
>>>>>> +
>>>>>> + When it is off, there will be no load balancing among CPUs on
>>>>>> + this cgroup. Tasks will stay in the CPUs they are running on
>>>>>> + and will not be moved to other CPUs.
>>>>>> +
>>>>>> + The initial value of this flag is "1". This flag is then
>>>>>> + inherited by child cgroups with cpuset enabled. Its state
>>>>>> + can only be changed on a scheduling domain cgroup with no
>>>>>> + cpuset-enabled children.
>>>>> [...]
>>>>>
>>>>>> + /*
>>>>>> + * On default hierachy, a load balance flag change is only
>>>>>> allowed
>>>>>> + * in a scheduling domain with no child cpuset.
>>>>>> + */
>>>>>> + if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
>>>>>> balance_flag_changed &&
>>>>>> + (!is_sched_domain(cs) || css_has_online_children(&cs->css)))
>>>>>> {
>>>>>> + err = -EINVAL;
>>>>>> + goto out;
>>>>>> + }
>>>>> The rule is actually
>>>>>
>>>>> - no child cpuset
>>>>> - and it must be a scheduling domain
> I always a bit confused by the usage of "scheduling domain", which
> overlaps with the SD concept from the scheduler standpoint.
It is supposed to mimic SD concept of scheduler.
>
> AFAIU a cpuset sched domain is not granted to be turned into an
> actual scheduler SD, am I wrong?
>
> If that's the case, why not better disambiguate these two concept by
> calling the cpuset one a "cpus partition" or eventually "cpuset domain"?
Good point. Peter has similar comment. I will probably change the name
and clarifying it better in the documentation.
Cheers,
Longman
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