Re: [PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups

From	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Newsgroups	linux.kernel
Subject	Re: [PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups
Date	2016-05-16 14:30 +0200
Message-ID	<rzpOO-71w-9@gated-at.bofh.it> (permalink)
References	<rznah-5ch-7@gated-at.bofh.it> <rzoJ4-6ey-25@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 16.05.2016 14:18, Peter Zijlstra wrote:
> On Mon, May 16, 2016 at 12:36:19PM +0300, Konstantin Khlebnikov wrote:
>> This feature allows to change cpu cgroup weight for a limited time.
>>
>> Cgroup interface:
>> cpu.cfs_reserve_us      - reserved time for each cpu.cfs_period_us
>> cpu.cfs_reserve_shares  - group weight during reserved time
>>
>> While cfs group consumes reserved cpu time it has different weight,
>> thus it gets different vruntime penalty for that execution.
>>
>>          ^ weight
>>          |
>>          |
>> reserve |
>> shares  -------*
>>          |      |
>>          |      |
>>          |      |
>> shares  -      *-----------------*
>>          |                        |
>>          |                        |
>>          0------|-----------------|-----------> time
>>                 reserve           quota
>>
>> Reserve can work as a "low limit": boost weight for "guaranteed" time,
>> and as a "high limit": give normal weight for a limited time and allow
>> utilize cpu when nobody else needs it.
>>
>
> You forgot to explain why I should care about this.

As I told this works as low-limit or high-limit which allow to
control cpu time distribution without hard limits and throttling.

Present quota/hard limit has well known problems when it throttle task
inside kernel where it holds mutexes. Also it's too strict and doesn't
allow utilization of unused cpu time.

-- 
Konstantin

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[PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2016-05-16 11:40 +0200
  [PATCH RFC 3/3] sched/fair: pulse-weight modulation controller for  cpu cgroup Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2016-05-16 11:40 +0200
  [PATCH RFC 1/3] sched/fair: call __refill_cfs_bandwidth_runtime  only for finite quota Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2016-05-16 11:40 +0200
  Re: [PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups Peter Zijlstra <peterz@infradead.org> - 2016-05-16 13:20 +0200
    Re: [PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups Peter Zijlstra <peterz@infradead.org> - 2016-05-16 14:30 +0200
    Re: [PATCH RFC 0/3] sched/fair: cpu time reserves for cgroups Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2016-05-16 14:30 +0200

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