I also tried to increase my interface MTU to 9000, but I am afraid that
netperf only transmits packets with less than 1500. Still investigating.
It may seem like picking a tiny nit, but netperf never transmits
packets. It only provides buffers of specified size to the stack. It is
then the stack which transmits and determines the size of the packets on
the network.
Drifting a bit more...
While there are settings, conditions and known stack behaviours where
one can be confident of the packet size on the network based on the
options passed to netperf, generally speaking one should not ass-u-me a
direct relationship between the options one passes to netperf and the
size of the packets on the network.
And for JumboFrames to be effective it must be set on both ends,
otherwise the TCP MSS exchange will result in the smaller of the two
MTU's "winning" as it were.
single CPU this can become a bottleneck. Does the test system have
multiple CPUs? Are IRQs for the multiple NICs balanced across
multiple CPUs?
Yes, this machine has 8 ppc 1.9Ghz CPUs. And the IRQs are balanced
across the CPUs, as I see in /proc/interrupts:
That suggests to me anyway that the dreaded irqbalanced is running,
shuffling the interrupts as you go. Not often a happy place for running
netperf when one want's consistent results.
# cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7
16: 940 760 1047 904 993 777 975 813 XICS Level IPI
18: 4 3 4 1 3 6
8 3 XICS Level hvc_console
19: 0 0 0 0 0 0
0 0 XICS Level RAS_EPOW
273: 10728 10850 10937 10833 10884 10788
10868 10776 XICS Level eth4
275: 0 0 0 0 0 0
0 0 XICS Level ehci_hcd:usb1, ohci_hcd:usb2, ohci_hcd:usb3
277: 234933 230275 229770 234048 235906 229858
229975 233859 XICS Level eth6
278: 266225 267606 262844 265985 268789 266869
263110 267422 XICS Level eth7
279: 893 919 857 909 867 917
894 881 XICS Level eth0
305: 439246 439117 438495 436072 438053 440111
438973 438951 XICS Level eth0 Neterion Xframe II 10GbE network
adapter
321: 3268 3088 3143 3113 3305 2982
3326 3084 XICS Level ipr
323: 268030 273207 269710 271338 270306 273258
270872 273281 XICS Level eth16
324: 215012 221102 219494 216732 216531 220460
219718 218654 XICS Level eth17
325: 7103 3580 7246 3475 7132 3394
7258 3435 XICS Level pata_pdc2027x
BAD: 4216
IMO, what you want (in the absence of multi-queue NICs) is one CPU
taking the interrupts of one port/interface, and each port/interface's
interrupts going to a separate CPU. So, something that looks roughly
like concocted example:
CPU0 CPU1 CPU2 CPU3
1: 1234 0 0 0 eth0
2: 0 1234 0 0 eth1
3: 0 0 1234 0 eth2
4: 0 0 0 1234 eth3
which you should be able to acheive via the method I think someone else
has already mentioned about echoing values into
/proc/irq/<irq>/smp_affinity - after you have slain the dreaded
irqbalance daemon.
rick jones
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