Re: Secret of great tcpdump performance ..

["Michael Krueger" <mickrulist () voipfuture com>]

On Tue, 22 Jan 2008 19:47:24 +0100, Rick Jones <rick.jones2 () hp com> wrote:

> How many processors do you have, are interrupts from each NIC going to  
> seperate processors/cores/whatever (show us the output of  
> /proc/interrupts), and have you bound each tcpdump to its corresponding  
> NICs interrupt CPU?
I have a single CPU / dual core machine. I think you are right. All of the  
interrupts are going to a single core:
lxvoipmon05:~/perftest # cat /proc/interrupts
           CPU0       CPU1
  0:        113  168298887    IO-APIC-edge  timer
  7:          1          1    IO-APIC-edge  parport0
  8:          0          2    IO-APIC-edge  rtc
  9:          0          0   IO-APIC-level  acpi
 14:          0    6034770    IO-APIC-edge  ide0
 50:          0   75531924   IO-APIC-level  libata, eth1
 58:          0     848554   IO-APIC-level  libata, ehci_hcd:usb1
 66:          0        394   IO-APIC-level  libata, ohci_hcd:usb2
 74:          0          3   IO-APIC-level  ohci1394
 82:          0   79599257   IO-APIC-level  eth0
177:          0    4140498   IO-APIC-level  eth2
NMI:          0          0
LOC:  168325561  168325456
ERR:          0
MIS:          0

This was without binding tcpdump to a specific CPU. Anyway, tcpdump was  
able to capture the traffic on both NICs without dropped packets. My own  
app almost immediatly reports dropped packets.

What do I have to do so that interrupts are handled on both cores? Will  
the interrupts move with the process if I bind them to separate cores?

--
Michael Krueger
VoIPFuture Ltd.
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