4.15 is now available in Bionic.  Marking this Fix Released.

** Tags added: kernel

** Information type changed from Private to Public

** Also affects: linux (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Bionic)
       Status: New => Fix Released

** Changed in: intel
       Status: New => Fix Released

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  [Feature] Increase percpu counter threshold size

Status in intel:
  Fix Released
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Bionic:
  Fix Released

Bug description:

  It was noted that the size of the percpu counters used for
  "node/zone_state" is only 8 bytes:

  struct per_cpu_pageset {
          struct per_cpu_pages pcp;
          s8 stat_threshold;
          s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];

  This code is very old. It effectively requires a pair hot, global
  cachelines to be touched when the per_cpu counter value does not fit
  in "vm_stat_diff".

  For this item, we need to increase the size of vm_stat_diff[] from an
  s8 to an s16, then allow the ->stat_threshold to be adjusted between
  the existing value of 125 and some larger value. Note that the current
  threshold from calculate_normal_threshold() is capped at 125 for all
  zones over 32GB. We have zones much larger than that today, so it is
  likely not scaling optimally.

  Target Kernel: 4.14
  Target Release: 18.04

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