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Subject[BUG] linux-2.6.28-rc3 regression: IRQ smp_affinities not respected
Hi all

One more problem it seems on 2.6.28-rc3

I wanted to get maximal throughput from my machine on a network bench with 3 Gigabit
links delivering 600.000 packets per second, so I tried to play with smp_affinity to
dedicate one CPU for each NIC.

It worked with 2.6.27, so there is a regression on this part.

Unfortunatly, git bisect is nearly impossible for me as after two steps
the resulting kernel doesnt event boot on this machine (same for oprofile
regression I mentioned earlier)

# grep eth1 /proc/interrupts
45: 20425 20418 20445 20441 20345 20349 20384 20397 PCI-MSI-edge eth1
# cat /proc/irq/45/smp_affinity
ff
# echo 1 >/proc/irq/45/smp_affinity
# cat /proc/irq/45/smp_affinity
01
# grep eth1 /proc/interrupts
45: 20928 20920 20943 20940 20845 20847 20887 20898 PCI-MSI-edge eth1
# grep eth1 /proc/interrupts
45: 21037 21030 21053 21049 20953 20956 20997 21007 PCI-MSI-edge eth1
# grep eth1 /proc/interrupts
45: 21141 21134 21156 21154 21057 21059 21101 21110 PCI-MSI-edge eth1

You can see interrupts keep being spreaded on all CPUS instead of CPU0 only.

That *kills* performance on high end routers and servers.

07:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708S Gigabit Ethernet (rev 12)
Subsystem: Hewlett-Packard Company NC373i Integrated Multifunction Gigabit Server Adapter
Flags: bus master, 66Mhz, medium devsel, latency 64, IRQ 45
Memory at fa000000 (64-bit, non-prefetchable) [size=32M]
[virtual] Expansion ROM at d1000000 [disabled] [size=16K]
Capabilities: [40] PCI-X non-bridge device.
Capabilities: [48] Power Management version 2
Capabilities: [50] Vital Product Data
Capabilities: [58] Message Signalled Interrupts: 64bit+ Queue=0/0 Enable+
bnx2 driver

Thanks


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