Public bug reported:

[Impact]
100Gbps network performance, as measured on an hns3 controller, doesn't scale 
as queue size goes up.

[Test Case]
Use a traffic generator instrument to generate load, using the SUT as an IP 
forwarder.

19.04 today:

8 queue 12 queue 16 queue 24 queue
37G 45G 38G 33G

With the patch applied:
8 queue 12 queue 16 queue 24 queue
37G 50G 47G 47G

[Fix]
14bd9a607f908 iommu/iova: Separate atomic variables to improve performance

[Regression Risk]
The patch makes no functional change, just reorders members of a structure. 
However, it is possible that this has unforeseen negative performance impacts 
on some platform.

** Affects: linux (Ubuntu)
     Importance: Undecided
     Assignee: dann frazier (dannf)
         Status: In Progress

** Affects: linux (Ubuntu Disco)
     Importance: Undecided
     Assignee: dann frazier (dannf)
         Status: In Progress

** Affects: linux (Ubuntu Eoan)
     Importance: Undecided
     Assignee: dann frazier (dannf)
         Status: In Progress

** Also affects: linux (Ubuntu Eoan)
   Importance: Undecided
     Assignee: dann frazier (dannf)
       Status: In Progress

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

** Changed in: linux (Ubuntu Disco)
       Status: New => In Progress

** Changed in: linux (Ubuntu Disco)
     Assignee: (unassigned) => dann frazier (dannf)

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https://bugs.launchpad.net/bugs/1832909

Title:
  Cache line contention prevents scaling of 100Gbps performance

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Disco:
  In Progress
Status in linux source package in Eoan:
  In Progress

Bug description:
  [Impact]
  100Gbps network performance, as measured on an hns3 controller, doesn't scale 
as queue size goes up.

  [Test Case]
  Use a traffic generator instrument to generate load, using the SUT as an IP 
forwarder.

  19.04 today:

  8 queue 12 queue 16 queue 24 queue
  37G 45G 38G 33G

  With the patch applied:
  8 queue 12 queue 16 queue 24 queue
  37G 50G 47G 47G

  [Fix]
  14bd9a607f908 iommu/iova: Separate atomic variables to improve performance

  [Regression Risk]
  The patch makes no functional change, just reorders members of a structure. 
However, it is possible that this has unforeseen negative performance impacts 
on some platform.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1832909/+subscriptions

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