Performance issue ( maybe )

Tom Schmitt TomSchmitt at
Mon Sep 6 07:01:07 UTC 2010

> Von: Bjarne Blichfeldt <bjb at>
> Betreff: Performance issue ( maybe )

> During clients startup, the servers takes a very long time  ~20-30 
> seconds> to answer a DISCOVER.

As a first step before you look for the source on the server, I would do a tcpdump on the server interface to make sure that the delay you are experiencing are really originate there and not somewhere else on the network.

> è Cpu2  :  0.0%us,  0.3%sy,  0.0%ni, 1.3%id,  98%wa,  0.0%hi,  0.0%si, 
> 0.0%st

So regarding the wait I/O: first step is looging without sync, second step is logging only errors and higher third step is no logging at all (only for a testperiod to see if your problem is going away)

> The only process really working is kjournald.

So are ther any other logmessages in high numbers beside the ones from dhcpd?

> 1)      anybody seen something similar ?

> 2)      Good ideas to further investigate ?  What about the network
> topology ? Any gotcha's when sending DISCOVERY through two cisco routers ?
Shouldn't be an isuue. I do the same without having problems.
Or did you you just upgrade your IOS?

Is the problem occuring on both on your dhcpd-servers at the same time? Or only on one of them?

And are there any messages in the log which could give you a hint?

> Also, what would be the consensus of disabling pingcheck ?
> ping-check false;
> The ping adds at least one  second to every discovery/offer,

You would win one second, but haveing other problems. I won't recomment it. Better you find the real problem than working around it.

>         option option-150 ;
>         filename "\\mboot.0<file:///\\mboot.0>" ;
>         next-server ;

Could it be, that not your server is the source of the problem, but the server

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