group.of.nepali.translators team mailing list archive

[Brian Murray <1801305@xxxxxxxxxxxxxxxxxx>]

Ubuntu 18.10 (Cosmic Cuttlefish) has reached end of life, so this bug
will not be fixed for that specific release.

** Changed in: linux (Ubuntu Cosmic)
       Status: Fix Committed => Won't Fix

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https://bugs.launchpad.net/bugs/1801305

Title:
  Restore request-based mode to xen-blkfront for AWS kernels

Status in linux-aws package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Committed
Status in linux-aws source package in Trusty:
  Fix Released
Status in linux source package in Xenial:
  Fix Committed
Status in linux-aws source package in Xenial:
  Fix Released
Status in linux source package in Bionic:
  Fix Committed
Status in linux-aws source package in Bionic:
  Fix Released
Status in linux source package in Cosmic:
  Won't Fix
Status in linux-aws source package in Cosmic:
  Fix Released
Status in linux source package in Disco:
  Won't Fix
Status in linux-aws source package in Disco:
  Fix Released

Bug description:
  In current Ubuntu kernels, PV blkfront drivers have blk-mq enabled by
  default and cannot use the old I/O scheduler.

  [Impact]
  blk-mq is not as fast as the old request-based scheduler for some workloads on HDD disks.

  [Fix]
  Amazon Linux has a commit which reintroduces the request-based mode. It disables blk-mq by default but allows it to be switched back on with a kernel parameter.

  For X this needs a small patch from upstream for error handling.

  For B/C this patchset is bigger as it includes the suspend/resume
  patches already in X, and a new fixup. These are desirable as the
  request mode patch assumes their presence.

  [Regression Potential]
  Could potentially break xen based disks on AWS.

  For B/C, the patches also add some code to the xen core around suspend
  and resume, this code is much smaller and also mirrors code already in
  Xenial.

  [Tests]
  Tested by AWS for Xenial, and their kernel engineers vetted the patches. I tested the Bionic and Cosmic patchsets with fio, the system appears stable and the IOPS promised for EBS Provisioned IOPS disks were met in my testing. I did an apt update/upgrade and everything worked (no hash-sum mismatches).

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