Re: Network performance degradation from 2.6.11.12 to 2.6.16.20

Jesper Dangaard Brouer wrote:

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Harry Edmon [off-list ref] wrote:

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I have a system with a strange network performance degradation from 
2.6.11.12 to most recent kernels including 2.6.16.20 and 
2.6.17-rc6. The system is has Dual single core Xeons with 
hyperthreading on.

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Hi Harry

Can you check which "high-res timesource" you are using?

In the kernel log look for:
 kernel: Using tsc for high-res timesource
 kernel: Using pmtmr for high-res timesource

I have experinced some network performance degradation when using the 
"pmtmr" timesource, on a Opteron AMD system.  It seems that the 
default timesource change between 2.6.15 to 2.6.16.

If you use "pmtmr" try to reboot with kernel option "clock=tsc".

On my Opteron AMD system i normally can route 400 kpps, but with 
timesource "pmtmr" i could only route around 83 kpps.  (I found the 
timer to be the issue by using oprofile).

We have CONFIG_HPET_TIMER=y, so we do not see these messages.