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

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

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.

Sample setup:

level   | shares      reserve shares
--------+----------------------------
high    | 1024*16     1024*16*16
normal  | 1024        1024*16
low     | 1024/16     1024

In this way cgroups are devided into three levels.
During reserved time they are promoted to the next level.

---

Konstantin Khlebnikov (3):
      sched/fair: call __refill_cfs_bandwidth_runtime only for finite quota
      sched/fair: copy taskgroup shares to each cfs_rq
      sched/fair: pulse-weight modulation controller for cpu cgroup

 kernel/sched/core.c  |   96 +++++++++++++++++++++++++++++++++++++++++++-----
 kernel/sched/fair.c  |  101 ++++++++++++++++++++++++++++++++++++++------------
 kernel/sched/sched.h |    5 ++
 3 files changed, 168 insertions(+), 34 deletions(-)