Messages in this thread | | | From | Xuewen Yan <> | Date | Sat, 5 Jun 2021 10:14:04 +0800 | Subject | Re: [PATCH] sched/uclamp: Avoid setting cpu.uclamp.min bigger than cpu.uclamp.max |
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On Sat, Jun 5, 2021 at 12:22 AM Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 04/06/2021 18:08, Qais Yousef wrote: > > On 06/03/21 10:24, Xuewen Yan wrote: > >> +CC Qais > > > > Thanks for the CC :) > > > >> > >> > >> Hi Quentin > >> > >> On Wed, Jun 2, 2021 at 9:22 PM Quentin Perret <qperret@google.com> wrote: > >>> > >>> +CC Patrick and Tejun > >>> > >>> On Wednesday 02 Jun 2021 at 20:38:03 (+0800), Xuewen Yan wrote: > >>>> From: Xuewen Yan <xuewen.yan@unisoc.com> > >>>> > >>>> When setting cpu.uclamp.min/max in cgroup, there is no validating > >>>> like uclamp_validate() in __sched_setscheduler(). It may cause the > >>>> cpu.uclamp.min is bigger than cpu.uclamp.max. > >>> > >>> ISTR this was intentional. We also allow child groups to ask for > >>> whatever clamps they want, but that is always limited by the parent, and > >>> reflected in the 'effective' values, as per the cgroup delegation model. > > > > As Quentin said. This intentional to comply with cgroup model. > > > > See Limits and Protections sections in Documentation/admin-guide/cgroup-v2.rst > > > > Specifically > > > > "all configuration combinations are valid" > > > > So user can set cpu.uclamp.min higher than cpu.uclamp.max. But when we apply > > the setting, cpu.uclamp.min will be capped by cpu.uclamp.max. I can see you > > found the cpu_util_update_eff() logic. > > To support this: > > Patrick had appropriate checks in his `[PATCH v10 12/16] sched/core: > uclamp: Extend CPU's cgroup controller`. > > https://lkml.kernel.org/r/20190621084217.8167-13-patrick.bellasi@arm.com > > But is was discussed that cgroup v2 `resource distribution model` > configurations (here protection/limit: uclamp_min/uclamp_max) should not > be restricted. > > Further down in this thread: > > "... Limits always trump protection in effect of course but please don't > limit what can be configured..."
Okay, I have got it. Thanks a lot!
BR xuewen.yan
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