On Thu, 10 Jan 2008 14:05:46 +0000
Jeba Anandhan <[EMAIL PROTECTED]> wrote:
> Hi All,
>
> If a server has multiple processors and N number of ethernet cards, is
> it possible to handle transmission by each processor separately? .In
> other words, each processor will be responsible for tx of few ethernet
> cards?.
>
>
>
> Example: Server has 4 processors and 8 ethernet cards. is it possible
> for each processor for transmission using 2 ethernet cards only?. So
> that, at a instant , data will be send out from 8 ethernet cards.
Hi Jeba
Modern ethernet cards have a big TX queue, so that even one CPU is enough
to keep several cards busy in //
You can check /proc/interrupts and change /proc/irq/*/smp_affinities to direct
IRQ to
particular cpus, but transmit is usually trigered by processes that might run
on different
cpus.
If all ethernet cards are on the same IRQ, then you might have a problem...
Example on a dual processor :
# cat /proc/interrupts
CPU0 CPU1
0: 11472559 74291833 IO-APIC-edge timer
2: 0 0 XT-PIC cascade
8: 0 1 IO-APIC-edge rtc
81: 0 0 IO-APIC-level ohci_hcd
97: 1830022231 847 IO-APIC-level ehci_hcd, eth0
121: 163095662 166443627 IO-APIC-level libata
NMI: 0 0
LOC: 85887285 85887193
ERR: 0
MIS: 0
You can see eth0 is on IRQ 97
Then :
# cat /proc/irq/97/smp_affinity
00000001
# echo 2 >/proc/irq/97/smp_affinity
# grep 97 /proc/interrupts
97: 1830035216 2259 IO-APIC-level ehci_hcd, eth0
# sleep 10
# grep 97 /proc/interrupts
97: 1830035216 5482 IO-APIC-level ehci_hcd, eth0
You can see only CPU1 is now handling IRQ 97 (but CPU0 is allowed to give to
eth0 some transmit work)
You might want to check /proc/net/softnet_stat too.
If your server is doing something very special (network trafic, no disk
accesses or number crunching),
you might need to bind application processes to cpus, not only network irqs.
process A, using nic eth0 & eth1, bound to CPU 0 (process and IRQs)
process B, using nic eth2 & eth3, bound to CPU 1
process C, using nic eth4 & eth5, bound to CPU 2
process D, using nic eth6 & eth7, bound to CPU 3
Also, take a look at "ethtool -c ethX" command
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