Re: About IO-APIC - General question

["Peter H. Koenig" <Peter.Koenig@phys.uni-paderborn.de>]

Hello,

Klaas, I would like to thank you for the data you provided.

From your first paragraph I take that there is the possibility of specifying
which processor(s) handle(s) interrupts manually.

Klaas Zweck wrote:
> i made some test on a linux-smp machine(kernel 2.4.9).
> i had one process just doing some calculation on prim numbers.
> i locked this to cpu 1 and disabled all interrupts on cpu 1.
> ( in fact i routed all to cpu 0 )
> then i started a make -j4 bzImage job in a remote
> shell to produce file i/o and network interrupts.
> i restricted all processes except the one doing the calculation
> from cpu 1 and delivered all interrupts only to cpu 0.

Is it neccessary specifying this for getting interrupt sharing working ?

My interrupts statistics table shows that the interrrupts are handled by
one
CPU solely:

$ cat /proc/interrupts 
           CPU0       CPU1       
  0:      84363          0    IO-APIC-edge  timer
  1:          2          0    IO-APIC-edge  keyboard
  2:          0          0          XT-PIC  cascade
  8:          1          0    IO-APIC-edge  rtc
 11:       1661          0   IO-APIC-level  eth0
 14:       8741          0    IO-APIC-edge  ide0
 15:          2          0    IO-APIC-edge  ide1
NMI:          0          0 
LOC:      84283      84281 
ERR:          0
MIS:          0

This differs somehow from the (old) IO-APIC documentation where in the
case
of SMP-boards the IRQ load is shared between the processors.

This problem occurs on a Supermicro P4DC6 using an unreleased bios
release
(without that so far the APIC has not been recognized at all), the MPS
specification set to version 1.1 in the bios using kernel 2.4.10, 2.4.17
and
2.4.18.

As some of the applications we run are quite Network or IO-intensive, we
would like to take advantage of the IRQ sharing.

Any suggestions ?

Pete



-- 
Dipl.-Chem. Peter H. Koenig                               
FB 6 - Theoretische Physik    Tel.: +49 5251 60 2332   
Universitaet Paderborn        Fax:  +49 5251 60 3435   
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