Re: _High_ CPU usage while routing (mostly) small UDP packets

Karsten Desler
2004-12-07T10:23:17Z

Karsten Desler <kdesler@soohrt.org> wrote:
> * jamal wrote:
> > Beats me. Make sure it boots NAPI. Also if you can turn off ITR; intel
> > loves to turn on that silly feature.
>
> ITR was in fact activated. I think i've disabled it now
> (e1000.InterruptThrottleRate=0 in the kernel cmdline).
> And as I'm reading the e1000 code, there is no way to enable/disable
> NAPI without a recompile. So the fact that ethtool spat out -NAPI in
> the version string means that NAPI is actually used.

But looking and the int/s number, I'm not so sure anymore. Is there any
other way to find out?

# ethtool -i eth0|grep ^vers
version: 5.5.4-k2-NAPI
# ethtool -i eth1|grep ^vers
version: 5.5.4-k2-NAPI

CPU0 CPU1
169: 5 115554253 IO-APIC-level eth0
177: 78998347 5568 IO-APIC-level eth1

# sar -I 169 5 5
11:20:05 INTR intr/s
11:20:10 169 10401.40
11:20:15 169 10579.80
11:20:20 169 10965.20
11:20:25 169 10768.20
11:20:30 169 10460.60
Average: 169 10635.04

# sar -I 177 5 5
11:18:50 INTR intr/s
11:18:55 177 4769.74
11:19:00 177 4780.80
11:19:05 177 4669.74
11:19:10 177 4724.55
11:19:15 177 4748.50
Average: 177 4738.67

Cheers,
Karsten