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

[Juerg Haefliger]

On Wed, 16 Oct 2019 17:15:36 -0400
Khalid Elmously <khalid.elmously at canonical.com> wrote:

> 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.

On condition that Kleber's feedback is addressed:
 
Acked-by: Juerg Haefliger <juergh at canonical.com>


> 
> 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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