Messages in this thread | | | Date | Mon, 19 Sep 2022 13:55:15 +0200 | Subject | Re: [PATCH v4 6/8] sched/fair: Add sched group latency support | From | Dietmar Eggemann <> |
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s/valentin.schneider@arm.com//
On 16/09/2022 10:03, Vincent Guittot wrote: > Task can set its latency priority, which is then used to decide to preempt > the current running entity of the cfs, but sched group entities still have > the default latency offset. > > Add a latency field in task group to set the latency offset of the > sched_eneities of the group, which will be used against other entities in
s/sched_eneities/sched_entity
> the parent cfs when deciding which entity to schedule first.
So latency for cgroups does not follow any (existing) Resource Distribution Model/Scheme (Documentation/admin-guide/cgroup-v2.rst)? Latency values are only used to compare sched entities at the same level.
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> +static int cpu_latency_write_s64(struct cgroup_subsys_state *css, > + struct cftype *cft, s64 latency) > +{
There is no [MIN, MAX] checking?
min_weight = sched_latency_to_weight[0] = -1024 max_weight = sched_latency_to_weight[39] = 973
[MIN, MAX] = [sysctl_sched_latency * min_weight >> NICE_LATENCY_SHIFT, sysctl_sched_latency * max_weight >> NICE_LATENCY_SHIFT]
With the `cpu.latency` knob user would have to know for example that the value is -24,000,000ns to get the same behaviour as for a task latency nice = -20 (latency prio = 0) (w/ sysctl_sched_latency = 24ms)?
For `nice` we have `cpu.weight.nice` next to `cpu.weight` in cgroup v2 ?
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