[Pkg-xen-devel] Bug#577788: dom0 kernels should suggest irqbalance

[Ian Campbell]

Control: reassign -1 src:linux
COntrol: retitle -1 SMP kernels should suggest irqbalance

On Thu, 2014-09-04 at 00:14 +0100, Ben Hutchings wrote:
> On Sun, 2014-08-31 at 03:10 +0100, Ian Campbell wrote:
> > (copying debian-kernel for reasons which will hopefully become obvious)
> > 
> > On Mon, 8 Jul 2013 18:10:58 +0200 =?UTF-8?Q?Moritz_M=C3=BChlenhoff?= <jmm at inutil.org> wrote:
> > > In current Debian kernel there's no special Xen dom0 kernel image and depending
> > > on irqbalance in the kernel package would be overkill.
> > 
> > Would it? I thought irqbalance is actually required even for native with
> > modern kernels, since the kernel doesn't do any balancing by itself (any
> > more, it did use to).
> 
> I don't know that it's generally required, but it can be useful if there
> is a lot of work done in interrupt or softirq context (and have multiple
> processors).
> 
> > Looking on my laptop for instance I see that all interrupts are going to
> > CPU0 out of the 4 processes. On the other hand my workstation does seem
> > to have balanced IRQs despite having no irqbalanced running, so I don't
> > know.
> > 
> > I reckon the kernel probably should recommend irqbalance these days, but
> > in any case there is no reason for Xen to do something different (since
> > IRQ balancing should work as on native).
> 
> At least kernels that support SMP could recommend it.

That sounds like a good idea to me.

Presumably irqbalanced is mostly harmless for UP kernels, but I think we
can avoid that recommends unless the auto-generation of debian/control
gets in the way too much. 

Ian.