Public bug reported:

[Impact]

When an instance in the AWS EC2 infrastructure is successfully
hibernated and resumed we want to deactivate the swap file as fast as
possible in order to make the instance available again for the user. By
default the kernel doesn't really optimize swapoff performance, it tries
to keep the whole system still usable and responsive while swapoff is
running.

However, in our specific use case, swapoff needs to complete as fast as
possible, so we may want to give swapoff I/O a higher priority and use
different heuristics in order to optimize the I/O and page readahead
generated by swapoff.

[Test Case]

Run the hibernation test on the AWS EC2 instances.

[Fix]

Apply a more aggressive swapin readahead policy that allows to improve
swapoff performance.

[Regression Potential]

Minimal, this change is only affecting the swapoff-related code and it
has been tested extensively with positive test results. The only
downside is that this different heuristic makes the system more
unresponsive during swapoff, but this is not a problem in the AWS
scenario, because (by explicit requirement) the user shouldn't be able
to use the instance during this swapoff phase.

** Affects: linux-aws (Ubuntu)
     Importance: Undecided
     Assignee: Andrea Righi (arighi)
         Status: New

** Affects: linux-aws (Ubuntu Bionic)
     Importance: Undecided
     Assignee: Andrea Righi (arighi)
         Status: New

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

** Changed in: linux-aws (Ubuntu)
     Assignee: (unassigned) => Andrea Righi (arighi)

** Changed in: linux-aws (Ubuntu Bionic)
     Assignee: (unassigned) => Andrea Righi (arighi)

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https://bugs.launchpad.net/bugs/1858618

Title:
  linux-aws: swapoff optimization

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