[SRU][PATCH 0/2][Bionic] Fix aggressive CFS throttling

[Khalid Elmously]

BugLink: https://bugs.launchpad.net/bugs/1832151

"sched/fair: Fix bandwidth timer clock drift condition" enabled CPU bandwidth "slice expiry" behaviour in cpu-local silos (something that should have been in effect all along but was basically completely broken). The undesired side-effect of this expirty being enabled is that threads of highly-threaded non-CPU-bound applications get throttled even when the application isn't using its full quota.

This fix eliminates the problem by removing cpu-local slice expiry altogether. A small pre-requisite patch makes the fix apply nicely.

A derivative 4.15 cloud kernel was tested with this fix and approved by the cloud provider, and I've tested this fix on the master 4.15 with positive results. 

More info in launchpad and salesforce.



Dave Chiluk (1):
  sched/fair: Fix low cpu usage with high throttling by removing
    expiration of cpu-local slices

Patrick Bellasi (1):
  sched/fair: Add lsub_positive() and use it consistently

 Documentation/scheduler/sched-bwc.txt | 74 +++++++++++++++++++-----
 kernel/sched/fair.c                   | 83 ++++++---------------------
 kernel/sched/sched.h                  |  4 --
 3 files changed, 79 insertions(+), 82 deletions(-)

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2.17.1