CFS Bandwidth Control v7

Hi all,

Please find attached the latest iteration of bandwidth control (v7).

This release continues the scouring started in v5 and v6, this time with attention paid to timers, quota expiration, and the reclaim path.

Thanks to Hidetoshi Seto for taking the time to review the previous series.

v7
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optimizations/tweaks:
- no need to reschedule on an enqueue_throttle
- bandwidth is reclaimed at time of dequeue rather than put_prev_entity, this prevents us losing small slices of bandwidth to load-balance movement.

quota/period handling:
- runtime expiration now handles sched_clock wrap
- bandwidth now reclaimed at time of dequeue rather than put_prev_entity, this was resulting in load-balance stranding small amounts of bandwidht perviously.
- logic for handling the bandwidth timer is now better unified with idle state accounting, races with period expiration during hrtimer tear-down resolved
- fixed wake-up into a new quota period waiting for timer to replenish bandwidth.

misc:
- fixed stats not being accumulated for unthrottled periods [thanks H. Sato]
- fixed nr_running corruption in enqueue/dequeue_task fair [thanks H. Sato]
- consistent specification changed to max(child bandwidth) <= parent bandwidth, sysctl controlling this behavior was nuked
- throttling not enabled until both throttle and unthrottle mechanisms are in place.
- bunch of minor cleanups per list discussion

Hideotoshi, the following patches changed enough, or are new, and should be looked over again before I can re-add your Reviewed-by.

[patch 04/16] sched: validate CFS quota hierarchies
[patch 06/16] sched: add a timer to handle CFS bandwidth refresh [patch 07/16] sched: expire invalid runtime
[patch 10/16] sched: throttle entities exceeding their allowed bandwidth [patch 15/16] sched: return unused runtime on voluntary sleep

Previous postings:
-----------------
v6: http://lkml.org/lkml/2011/5/7/37
v5: http://lkml.org/lkml/2011/3 /22/477
v4: http://lkml.org/lkml/2011/2/23/44
v3: http://lkml.org/lkml/2010/10/12/44:
v2: http://lkml.org/lkml/2010/4/28/88
Original posting: http://lkml.org/lkml/2010/2/12/393
Prior approaches: http://lkml.org/lkml/2010/1/5/44 ["CFS Hard limits v5"]

Let me know if anything's busted :)

- Paul