Hi, Kumar, 1) Regarding rx queues: what does "ls /sys/class/net/eth0/queues" show ? 2) can you try setting affinity for working only with CPU3 and see what happens after some traffic is sent by cat /proc/interrupts? regards, Rami Rosen http://ramirose.wix.com/ramirosen On Tue, Mar 26, 2013 at 8:31 PM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
Hi All,
I was reading some stuff on interrupts and irq lines today and I thought I'll expermient with the network rx path. To start with, I've a Virtual Machine running 3.8 linux kernel. My machine has 4 CPU cores, network (eth) interface is driven by pcnet_32 AMD driver and is tied to IRQ line #19. I started some network traffic and I notice that out of those 4 CPUs, only one of them is being used and despite changing the CPU affinity, I still don't see the other cores being used for this network traffic. So based on this behavior(please see the logs below), I've these following queries: i) Does it mean that this network card do not have multiple Rx Queues ? ii) I think all the modern NICs must be implementing multiple Rx Queues and hence Can someone please point me to the simplest of such implemenation in any of the in-tree drivers ? iii) I'm just doing a simple 'ping' to google with of big size packets, As I do not have a peer to use packetgen/netperf/iperf utilities.
ref: Comments in double quotes. <logs> $ uname -r 3.8.0-rc6-next-20130208
$ cat /proc/cpuinfo |grep processor processor : 0 processor : 1 processor : 2 processor : 3 "Total 4 cpu cores"
$ cat /proc/interrupts|egrep 'eth0|CPU' CPU0 CPU1 CPU2 CPU3 19: 5103 74 33 5 IO-APIC-fasteoi eth0 "IRQ Line #19 for the network device"
$ lspci|grep -i ethernet 02:01.0 Ethernet controller: Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE] (rev 10)
"AMD NIC" $ lspci -s 02:01.0 -vvv|grep module Kernel modules: pcnet32
$ lsmod|grep pcnet32 pcnet32 40671 0 "driver"
# whoami root
# cat /proc/irq/19/smp_affinity 03
# cat /proc/irq/19/affinity_hint 00
"I think smp_affinity is a bit map, therefore for all the four cores to be utilized, all 4 bits should be set to 1, which leads to 15(0xf), hence Chaning the cpu affinity" # echo 15 > /proc/irq/19/smp_affinity # cat /proc/irq/19/smp_affinity 15
"started network traffic here and monitoring it" # cat /proc/interrupts|grep eth0 19: 5452 78 33 5 IO-APIC-fasteoi eth0 # cat /proc/interrupts|grep eth0 19: 5488 78 35 5 IO-APIC-fasteoi eth0 # cat /proc/interrupts|grep eth0 19: 5492 78 35 5 IO-APIC-fasteoi eth0 # cat /proc/interrupts|grep eth0 19: 5500 78 35 5 IO-APIC-fasteoi eth0 ................................. .........after some time......... # cat /proc/interrupts|grep eth0 19: 6035 78 42 5 IO-APIC-fasteoi eth0
"Most of the packets are still getting routed through CPU0 *Only*." <logs>
-Amit
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies