Re: IRQ Routing. [A 2.6 question about smp irq balancing]

[Paul <set@pobox.com>]

"Martin J. Bligh" <mbligh@aracnet.com>, on Mon Oct 20, 2003 [07:23:44 AM] said:
> > Are their any linux tools to allow the user to view irq routing details, 
> > and maybe change the routing after boot ?
> > 
> > This might be useful in special cases.
> 
> Yeah, "cat /proc/interrupts" and 
> "echo <cpu_bitmask> > /proc/irq/<number>/smp_affinity"
> 
> M.

	Hi;

	Here is my /proc/interrupts for 2.6.0-test6:

           CPU0       CPU1       
  0:      10442 1795758405    IO-APIC-edge  timer
  1:     737209          0    IO-APIC-edge  i8042
  2:          0          0          XT-PIC  cascade
  3:        517          1    IO-APIC-edge  serial
  4:  100488033          1    IO-APIC-edge  serial
  5:          0          0    IO-APIC-edge  eth0
  8:          2          0    IO-APIC-edge  rtc
 12:    1626560          1    IO-APIC-edge  i8042
 14:    8988748          8    IO-APIC-edge  ide0
 15:     377275          1    IO-APIC-edge  ide1
 16:    1364704          2   IO-APIC-level  eth1
 17:     857789     144630   IO-APIC-level  eth2
 19:     165579          1   IO-APIC-level  Ensoniq AudioPCI
NMI: 1795768424 1795763795 
LOC: 1795877980 1795878044 
ERR:          0
MIS:        351

	Now, on 2.4 kernels, both columns are about even.
Upon noticing this, I tried to get more interrupts on cpu1.
You can see I got some on eth2, by running many 'ping -f's at the
same time. I havent been able to get anything more out of ide[01]
for cpu1, even though Ive run many -j4 compiles of huge packages,
which coincided with other things that bring my load up to 8+ over
the course of 20 days of uptime. /proc/irq/<num>/smp_affinity
is 3 (ie. both cpus) for all <num>. I was able to induce interrupts
on cpu1 for ide0 by setting it to 2.
	Ok, my question is, is this how it is supposed to be?
I ask because I am seeing a throughput decrease on 2.6 v 2.4
on hdparm -t, bonnie, kernel compile benchmarks, though interactivity
seems to be better.

Paul
set@pobox.com