On Tuesday 26 August 2008, Evgeniy Polyakov wrote:

On Tue, Aug 26, 2008 at 10:44:56PM +0200, Eric Dumazet (dada1@cosmosbay.com) 

wrote:

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Do you have any packet sockets in this system? Like running dhcp daemon?

No, nothing at all.

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Another way to see this problem can be to start a sniffer on the machine,
even with a restrictive pcap filter, to check if performance change or
not. (It should decrease)

Yes, when i run tcpdump even without promisc at peak time, machine will be 
almost dead. Transit traffic will be 100ms+. I know that it is timestamping 
packets. Same almost for any libpcap app.

Or just check /proc/net/packet iirc.
Anyway, having at least one packet socket ends up with timestamping of
each packet, so you will get fair load of getnstimeofday() in that case.

There is very short list of tasks. Attached. 
/proc/net/packet clean, nothing there.

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For example, I believe that running "ping" could have the same effect
(increasing netstamp_needed variable : every incoming packet has to be
timestamped)

Even answering icmp timestamp request will take resources.

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So beware of pings, traceroute and other networking tools...

When i am measuring performance - they are all off.

Yup, this innocent toys can end up with this such behaviour on modern
highly loaded machines.