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[Bug 1592809] Re: Restore irqfd fast path for PPC


------- Comment From jhopper@xxxxxxxxxx 2016-06-30 10:07 EDT-------
I was able to verify the proposed (host) kernel improves guest performance with some uperf testing. Thanks!

For example:
single VM to VM; TCP_RR - 1 byte, 4 instances

stable kernel (4.4.0-28):

proposed kernel (4.4.0-29):

Although I am curious, I tried to look at the source:
apt-get install linux-source/xenial-proposed

I don?t see this patch in that source, but maybe that is expected since
its only shown as ?4.4.0??  /usr/src/linux-source-4.4.0.tar.bz2

** Tags removed: verification-needed-xenial
** Tags added: verification-done-xenial

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  Restore irqfd fast path for PPC

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Xenial:
  Fix Committed
Status in linux source package in Yakkety:
  Fix Released

Bug description:
  Dear Canonical,

  A patch is now upstream to restore the irqfd fast path for Power, can
  this be pulled into a 16.04.1? It was found to significantly help
  guest small msg rate networking performance by ~30%.

  Commit id:

    KVM: PPC: Book3S HV: Re-enable XICS fast path for irqfd-generated

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