[Bug 2045708] Re: Improve debian/99-gce.rules to set schedulers based on disk

[Chloé Smith]

** Description changed:

  We should reduce the `udev` rule scope here and change I/O scheduler.
  The previous `udev` rule was drastically reducing the bootspeed on SSD
  backed instances, as the `noop` scheduler is pretty old school.
  
  I did pretty extensive experimentation and found that swapping to "none"
  in this file yielded the best results on HDD instances (>10s improvement
  in boot time on average). Letting SSD's just roll independently also
  seemed to give the best speeds.
- 
- [ Test Plan ]
- 
-  * I built test GCP images with this file changed as proposed [0]
-    * This can be done with a PPA hooked into CPC bootstrap scripts (kajiya's here: [1])
- 
- [ Where problems could occur ]
- 
-  * I can't see any regressions happening as we're moving _from_ `noop` _to_ not using a scheduler at all
-    (`none`), which was the original behaviour before this file was introduced.
- 
- SRU
- ====
  
  [ Impact ]
  
   * If an end user launches an Ubuntu instance in GCE backed with a HDD, no
     scheduler will be used natively.
  
   * This package is provided upstream by Google themselves, and is part of a
     collection of tools and that ensures that the Ubuntu images published to GCE
     run properly on the platform.
  
  [Test Case]
  
  When this package lands in -proposed, the following will happen:
  
   * an image built with this package from -proposed will be built for GCE and
     published in the `ubuntu-os-cloud-image-proposed` project
   * The image will go through CPC's own CTF framework, and assuming it passes
     will be handed to the Google team to perform their own verification.
+  * This can also be done independently with a PPA hooked into CPC's bootstrap 
+    scripts (kajiya's PPA here: [0])
  
  If all the testing indicates that the image containing the new package
  is good, verification is considered finished.
  
- [0]: https://code.launchpad.net/~kajiya/ubuntu/+source/gce-compute-image-packages/+git/gce-compute-image-packages/+merge/455766
- [1]: https://launchpad.net/~kajiya/+archive/ubuntu/gce-compute-image-packages
+ [0]: https://launchpad.net/~kajiya/+archive/ubuntu/gce-compute-image-
+ packages

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https://bugs.launchpad.net/bugs/2045708

Title:
  Improve debian/99-gce.rules to set schedulers based on disk

Status in gce-compute-image-packages package in Ubuntu:
  Fix Released

Bug description:
  We should reduce the `udev` rule scope here and change I/O scheduler.
  The previous `udev` rule was drastically reducing the bootspeed on SSD
  backed instances, as the `noop` scheduler is pretty old school.

  I did pretty extensive experimentation and found that swapping to
  "none" in this file yielded the best results on HDD instances (>10s
  improvement in boot time on average). Letting SSD's just roll
  independently also seemed to give the best speeds.

  [ Impact ]

   * If an end user launches an Ubuntu instance in GCE backed with a HDD, no
     scheduler will be used natively.

   * This package is provided upstream by Google themselves, and is part of a
     collection of tools and that ensures that the Ubuntu images published to GCE
     run properly on the platform.

  [Test Case]

  When this package lands in -proposed, the following will happen:

   * an image built with this package from -proposed will be built for GCE and
     published in the `ubuntu-os-cloud-image-proposed` project
   * The image will go through CPC's own CTF framework, and assuming it passes
     will be handed to the Google team to perform their own verification.
   * This can also be done independently with a PPA hooked into CPC's bootstrap 
     scripts (kajiya's PPA here: [0])

  If all the testing indicates that the image containing the new package
  is good, verification is considered finished.

  [0]: https://launchpad.net/~kajiya/+archive/ubuntu/gce-compute-image-
  packages

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