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

[Daniel Axtens]

Hi Kleber,

Sorry, just replied to your other email - yes, the patches from the
SRPM were never upstream and should therefore be marked as SAUCE. I
didn't do that because I (mistakenly!) thought that was limited to
patches written specifically for the Ubuntu kernel.

Regards,
Dniel
On Wed, Nov 7, 2018 at 7:52 PM Kleber Souza <kleber.souza at canonical.com> wrote:
>
> On 11/02/18 09:57, 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(-)
> >
> Hi Daniel,
>
> The patches come from "AWS 4.14 kernel SRPM", does it mean they were
> never upstream? If that's the case we need to mark the patches as SAUCE
> (we could do it when applying them).
>
>
> Thanks,
>
> Kleber
>