Re: [PATCH] 2.5.31 Summit NUMA patch with dynamic IRQ balancing

[James Cleverdon <jamesclv@us.ibm.com>]

On Friday 23 August 2002 05:29 pm, Grover, Andrew wrote:
> > From: James Cleverdon [mailto:jamesclv@us.ibm.com]
> >
> > > This should be moved to acpi.h
> >
> > Will be, once I'm sure this is the right way to go.  As
> > mentioned earlier, I'm
> > having ACPI problems that seem to imply ACPI isn't building
> > the full IRQ
> > table.  In 2.4 we could let MPS do this.  Maybe 2.5 will need
> > to revert to
> > that behavior.
>
> What happens when you use the FULL ACPI support? I suspect that you really
> do want the interpreter, in order to evaluate _PRTs properly.
>
> ISTR that the reason you are thinking that ACPI only is programming some of
> the ioapic entries is because whatever is printing them is looking at the
> mp_irqs array. Which is MPS specific. So ACPI doesn't bother filling it all
> in. :)
>
> Is that a bug? Should ACPI fill it in completely, or maybe not at all?
> Don't know. But it is strictly unnecessary.
>
> Regards -- Andy

Bingo!  With full ACPI turned on, the system does indeed boot.  The extra I/O 
APIC entries are being programmed from the PRT.

(Call chain is:  pci_acpi_init --> acpi_pci_irq_init --> mp_parse_prt --> 
io_apic_set_pci_routing)

So, given that quite a number of our customers would like to run with 
hyperthreading turned on, but do not want full ACPI, what is the right thing 
to do in the HT-only case?  Add extra code to process the PRT?  Fall back on 
MPS's IRQ records?  Something else entirely?

-- 
James Cleverdon
IBM xSeries Linux Solutions
{jamesclv(Unix, preferred), cleverdj(Notes)} at us dot ibm dot com