On Tue, Mar 26, 2013 at 09:31:01PM +0200, Rami Rosen wrote:
> Hi,
>
> 1) You can be sure that it does not use more than one rx queue.
>
> You can find more info about RX queues in
> http://media.wix.com/ugd//295986_4ef6dbdf11fd0a7f74f09741b4b5b2ee.pdf
>
> (I wrote it, a shameless plug...)
>
> 2) Does the irqbalance service, which is common in some distros, is
> running ? can you try to disable it and run traffic again and check
> /proc/interrupts afrer some time ?
>
> 3) regardless of 2 (meaning not stopping irqbalance if it was active)
> can you please try "taskset 02 ping www.google.com" and tell us
> whether interrupts were incremented on the second CPU ? (please send
> /proc/interrupts | grep eth0 before and after sending, let's say, 5
> pings)?
>
My apologies for responding after a long time. I lost access to the machine on
which this VM was running. Now running this VM on my laptop, which seem to have
similar hardware configuration. Please find the details, which you had asked for
below:(comment in quotes)
amit@ubuntu:~$ cat /proc/cpuinfo |grep processor
processor : 0
processor : 1
"2 CPU"
amit@ubuntu:~$ cat /proc/interrupts |egrep 'CPU|eth0'
CPU0 CPU1
19: 7887 31 IO-APIC-fasteoi eth0
amit@ubuntu:~$ ls -lah /sys/class/net/eth0/device/driver
lrwxrwxrwx 1 root root 0 Mar 29 01:13 /sys/class/net/eth0/device/driver ->
../../../../bus/pci/drivers/pcnet32
amit@ubuntu:~$ lsmod|grep -i pcnet32
pcnet32 40671 0
"driver"
amit@ubuntu:~$ ls /sys/class/net/eth0/queues
rx-0 tx-0
"just one rx-queue"
amit@ubuntu:~$ sudo cat /proc/irq/19/smp_affinity
01
"tied to CPU0"
"disabling irqbalance"
amit@ubuntu:~$ status irqbalance
irqbalance start/running, process 1016
amit@ubuntu:~$ sudo stop irqbalance
irqbalance stop/waiting
amit@ubuntu:~$ taskset 02 ping www.google.com
"after sometime"
amit@ubuntu:~$ cat /proc/interrupts |egrep 'CPU|eth0'
CPU0 CPU1
19: 8046 31 IO-APIC-fasteoi eth0
"No increase in interrupt counts on CPU1"
"Now lets use both CPUs"
root@ubuntu:/home/amit# echo "3" >/proc/irq/19/smp_affinity
root@ubuntu:/home/amit# cat /proc/irq/19/smp_affinity
03
"As before, start ping and expecting both CPUs to be used"
amit@ubuntu:~$ taskset 02 ping www.google.com
root@ubuntu:/home/amit# cat /proc/interrupts |egrep 'CPU|eth0'
CPU0 CPU1
19: 9001 71 IO-APIC-fasteoi eth0
^^^^
and yes, indeed..
So multiple Rx queues seem to have nothing to do with CPU affinity, as in this
case I have a driver implementing a single Rx queue and I see that the rx packet
processing happens through both of the CPUs.
-Amit
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