Messages in this thread |  | | From | Vincent Guittot <> | Date | Wed, 12 Oct 2022 17:42:46 +0200 | Subject | Re: [PATCH v5 5/7] sched/fair: Add sched group latency support |
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On Wed, 12 Oct 2022 at 16:22, Qais Yousef <qais.yousef@arm.com> wrote: > > On 09/25/22 16:39, Vincent Guittot wrote: > > Task can set its latency priority with sched_setattr(), which is then used > > to set the latency offset of its sched_entity, but sched group entities > > still have the default latency offset value. > > > > Add a latency.nice field in cpu cgroup controller to set the latency > > priority of the group similarly to sched_setattr(). The latency priority > > is then used to set the offset of the sched_entities of the group. > > > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > --- > > Documentation/admin-guide/cgroup-v2.rst | 8 ++++ > > kernel/sched/core.c | 53 +++++++++++++++++++++++++ > > kernel/sched/fair.c | 33 +++++++++++++++ > > kernel/sched/sched.h | 4 ++ > > 4 files changed, 98 insertions(+) > > > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > > index be4a77baf784..d8ae7e411f9c 100644 > > --- a/Documentation/admin-guide/cgroup-v2.rst > > +++ b/Documentation/admin-guide/cgroup-v2.rst > > @@ -1095,6 +1095,14 @@ All time durations are in microseconds. > > values similar to the sched_setattr(2). This maximum utilization > > value is used to clamp the task specific maximum utilization clamp. > > > > + cpu.latency.nice > > + A read-write single value file which exists on non-root > > + cgroups. The default is "0". > > + > > + The nice value is in the range [-20, 19]. > > + > > + This interface file allows reading and setting latency using the > > + same values used by sched_setattr(2). > > I still don't understand how tasks will inherit the latency_nice value from > cgroups they're attached to.
The behavior is the same as for sched_entity weight. The latency is applied on the sched_entity of the group
> > For example, in EAS path we operate at task level only. If the task's > p->latency_nice = 0, but it belongs to a task group tg->latency_nice = -19; > what should the task's latency_nice be in this case? If it's in a hierarchy, > how would the effective value be calculated? > > > Thanks > > -- > Qais Yousef
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