Re: Regression: Bisected, IRQ and MSI allocations screwed without sparse irq

Jesper Dangaard Brouer
2008-11-21T10:33:38Z

On Thu, 2008-11-20 at 16:34 -0800, Thomas Gleixner wrote:
> On Thu, 20 Nov 2008, Jesper Dangaard Brouer wrote:
> > I have bisected a regression to your commit
> > 3235e936c0cc3589309280b6f59e5096779adae3,
> > "x86: remove sparse irq from Kconfig".
> >
> > Its actually not necessary your fault, as your commit simply removes
> > the config option HAVE_SPARSE_IRQ. This revels the bug / regression
> > I'm exposted to.
>
> Yup, the bisect result is pretty useless.
>
> > The cause of this problem (tracked down together with Robert Olsson)
> > is that on 2.6.28 I have a lot less IRQs available. It seems max 34
> > IRQs. Due the reduced number of IRQs the NIU driver cannot get
> > enough IRQs to the interfaces, and starts to use "IO-APIC" based
> > IRQs.
>
> Can you please try the attached patch ?

I have tried the patch and it solved the problem! :-)

I'll gladly test other patches from your. Guess this patch needs to be
brushed up before a mainline patch is ready.

My hardware is a HP ProLiant DL380-G5.

> -----
> arch/x86/kernel/io_apic.c | 22 +---------------------
> 1 file changed, 1 insertion(+), 21 deletions(-)
>
> Index: linux-2.6/arch/x86/kernel/io_apic.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/io_apic.c
> +++ linux-2.6/arch/x86/kernel/io_apic.c
> @@ -3594,27 +3594,7 @@ int __init io_apic_get_redir_entries (in
>
> int __init probe_nr_irqs(void)
> {
> - int idx;
> - int nr = 0;
> -#ifndef CONFIG_XEN
> - int nr_min = 32;
> -#else
> - int nr_min = NR_IRQS;
> -#endif
> -
> - for (idx = 0; idx < nr_ioapics; idx++)
> - nr += io_apic_get_redir_entries(idx) + 1;
> -
> - /* double it for hotplug and msi and nmi */
> - nr <<= 1;
> -
> - /* something wrong ? */
> - if (nr < nr_min)
> - nr = nr_min;
> - if (WARN_ON(nr > NR_IRQS))
> - nr = NR_IRQS;
> -
> - return nr;
> + return NR_IRQS;
> }
>

--
Med venlig hilsen / Best regards
Jesper Brouer
ComX Networks A/S
Linux Network developer
Cand. Scient Datalog / MSc.
Author of http://adsl-optimizer.dk
LinkedIn: http://www.linkedin.com/in/brouer