APPLIED/cmnt: [SRU bionic-aws][PATCH 0/6] LP: #1801305: xen-blkfront: restore request mode

[Khaled Elmously]

Applied to bionic-aws/master. Added "SAUCE: " to all patches

On 2018-11-02 20:00:04 , Daniel Axtens wrote:
> 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 Xenial
> 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).
> 
> Anchal Agarwal (1):
>   xen-blkfront: Fixed blkfront_restore to remove a call to negotiate_mq
> 
> Munehisa Kamata (5):
>   xen/manage: keep track of the on-going suspend mode
>   xen/manage: introduce helper function to know the on-going suspend
>     mode
>   xenbus: add freeze/thaw/restore callbacks support
>   xen-blkfront: add callbacks for PM suspend and hibernation
>   xen-blkfront: resurrect request-based mode
> 
>  drivers/block/xen-blkfront.c      | 475 ++++++++++++++++++++++++++----
>  drivers/xen/manage.c              |  73 +++++
>  drivers/xen/xenbus/xenbus_probe.c | 102 ++++++-
>  include/xen/xen-ops.h             |   4 +
>  include/xen/xenbus.h              |   3 +
>  5 files changed, 576 insertions(+), 81 deletions(-)
> 
> -- 
> 2.17.1
> 
> 
> -- 
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