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Groups > linux.debian.kernel > #63838

Bug#926967: Don't recommend irqbalance (was: Re: Handling irqbalance in virtual environments)

Cross-posted to 2 groups.

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Package: src:linux
Version: 4.19.28-2
Severity: important

On Fri, Apr 12, 2019 at 09:10:32PM +0100, Ben Hutchings wrote:
> On Fri, 2019-04-12 at 10:53 +0200, Bastian Blank wrote:
> > It turns out we got again problems with irqbalance.
> > 
> > It was added as recommends of the main image in 3.16, as it was reported
> > that older kernels move all interrupts to CPU 0 without help.[1]
> > 
> > In the meantime the kernel can do balancing on it's own.  In 4.9, I've
> > seen it working with aacraid, each queue gets hard pinned to it's own
> > CPU from 0 to $NRCPUS.  In 4.19 I've seen the same working properly with
> > virtio-net.
> > 
> > With 4.19, even on real hardware, where interrupts have an affinity for
> > all cpus, each interrupt is actually delivered to different cpu.
> > 
> > Random example for this, it even selects only one thread of each core:
> > 
> > >  26:    0    0    0    0   92    0    0    0  IR-PCI-MSI 3670017-edge      eno1-TxRx-0
> > >  27:    0    0    0    0    0  167    0    0  IR-PCI-MSI 3670018-edge      eno1-TxRx-1
> > >  28:    0    0    0    0    0    0  467    0  IR-PCI-MSI 3670019-edge      eno1-TxRx-2
> > >  29:    0    0    0    0    0    0    0  454  IR-PCI-MSI 3670020-edge      eno1-TxRx-3
> > 
> > Now irqbalance comes to re-do the existing pinning, and the result is not
> > longer correct but $RANDOM for the hard queue-to-cpu case of virtio.
> 
> Then let's drop the recommendation.

Okay.

Regards,
Bastian

-- 
I'm a soldier, not a diplomat.  I can only tell the truth.
		-- Kirk, "Errand of Mercy", stardate 3198.9

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Thread

Handling irqbalance in virtual environments Bastian Blank <waldi@debian.org> - 2019-04-12 11:10 +0200
  Re: Handling irqbalance in virtual environments Bastian Blank <waldi@debian.org> - 2019-04-12 11:40 +0200
  Re: Handling irqbalance in virtual environments Ben Hutchings <ben@decadent.org.uk> - 2019-04-12 22:20 +0200
    Bug#926967: Don't recommend irqbalance (was: Re: Handling irqbalance in virtual environments) Bastian Blank <waldi@debian.org> - 2019-04-12 23:10 +0200
      Bug#926967: Don't recommend irqbalance (was: Re: Handling irqbalance in virtual environments) Nicholas D Steeves <nsteeves@gmail.com> - 2019-04-15 01:00 +0200
      Bug#926967: Don't recommend irqbalance (was: Re: Handling irqbalance in virtual environments) Bastian Blank <waldi@debian.org> - 2019-04-23 21:50 +0200
      Processed: Re: Bug#926967: Don't recommend irqbalance (was: Re:  Handling irqbalance in virtual environments) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2019-04-23 21:50 +0200

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