Messages in this thread | | | Subject | Re: [PATCH] sched: cgroup SCHED_IDLE support | From | Dietmar Eggemann <> | Date | Fri, 11 Jun 2021 18:43:04 +0200 |
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On 10/06/2021 21:14, Josh Don wrote: > Hey Dietmar, > > On Thu, Jun 10, 2021 at 5:53 AM Dietmar Eggemann > <dietmar.eggemann@arm.com> wrote: >> >> Any reason why this should only work on cgroup-v2? > > My (perhaps incorrect) assumption that new development should not > extend v1. I'd actually prefer making this work on v1 as well; I'll > add that support. > >> struct cftype cpu_legacy_files[] vs. cpu_files[] >> >> [...] >> >>> @@ -11340,10 +11408,14 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, >>> >>> static DEFINE_MUTEX(shares_mutex); >>> >>> -int sched_group_set_shares(struct task_group *tg, unsigned long shares) >>> +#define IDLE_WEIGHT sched_prio_to_weight[ARRAY_SIZE(sched_prio_to_weight) - 1] >> >> Why not 3 ? Like for tasks (WEIGHT_IDLEPRIO)? >> >> [...] > > Went back and forth on this; on second look, I do think it makes sense > to use the IDLEPRIO weight of 3 here. This gets converted to a 0, > rather than a 1 for display of cpu.weight, which is also actually a > nice property.
I'm struggling to see the benefit here.
For a taskgroup A: Why setting A/cpu.idle=1 to force a minimum A->shares when you can set it directly via A/cpu.weight (to 1 (minimum))?
WEIGHT cpu.weight tg->shares
3 0 3072
15 1 15360
1 10240
`A/cpu.weight` follows cgroup-v2's `weights` `resource distribution model`* but I can only see `A/cpu.idle` as a layer on top of it forcing `A/cpu.weight` to get its minimum value?
*Documentation/admin-guide/cgroup-v2.rst
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