Re: [RFC/PATCHv2] x86/irq: round-robin distribution of irqs to cpusw/in node

From: Thomas Gleixner
Date: Wed Sep 29 2010 - 14:06:23 EST


On Wed, 29 Sep 2010, Arthur Kepner wrote:
> On Mon, Sep 27, 2010 at 05:17:07PM -0700, Eric W. Biederman wrote:
> > Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes:
>
> On Tue, Sep 28, 2010 at 03:59:33AM -0700, Eric W. Biederman wrote:
> > Thomas Gleixner <tglx@xxxxxxxxxxxxx> writes:
> >
> > > On Mon, 27 Sep 2010, Eric W. Biederman wrote:
> > >> > On Mon, 27 Sep 2010, Arthur Kepner wrote:
> > >> The deep bug is that create_irq_nr allocates a vector (which it does
> > >> because at the time there was no better way to mark an irq in use on
> > >> x86). In the case of msi-x we really don't know the node that irq is
> > >> going to be used on until we get a request irq. We simply know which
> > >> node the device is on.
> > >
> > > Bah. So the whole per node allocation business is completely useless
> > > at this point.
> >
> > Probably.
>
> Huh? No, the patch that started this thread spreads the irqs around
> and avoids the problem of a single CPU's vectors all being consumed.

I'm talking about the per node memory allocations for sparse. Not the
irq vectors

> >
> > Understood. It has taken a couple of years before this bug finally
> > bit anyone waiting a release or two to get it fixed properly seems
> > reasonable.
> > ....
>
> And so what are we to do in the meantime? At the moment we're
> disabling MSIX, which is a pretty unattractive workaround.

I understand that. The cleanup patches are hopefully ready for the
next kernel, so we can deal with that problem on top of them.

Thanks,

tglx
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