Intel EM tuning (PT1000 adaptors)

[Mike Tancsa]

At 12:30 PM 1/30/2007, Jack Vogel wrote:

>Performance tuning is not something that I have yet had time to focus
>on, our Linux team is able to do a lot more of that. Just at a glance,
>try increasing your mbuf pool size and the number of receive descriptors
>for a start.


OK, I setup a test box the pass packets through and I am getting 
results I dont understand.  Increasing hw.em.rxd in loader.conf (and 
rebooting each time), I am getting worse results.

With hw.em.rxd=4096
Jan 30 17:19:10 em-test kernel: em0: Receive No Buffers = 5707564

With hw.em.rxd=1024
Jan 30 17:22:31 em-test kernel: em0: Receive No Buffers = 351


With hw.em.rxd=512
Jan 30 17:27:24 em-test kernel: em0: Receive No Buffers = 230

with default 256

Jan 30 16:55:44 em-test kernel: em0: Receive No Buffers = 77


with 128, its gets much worse.  This is with a stock UP kernel, no 
INET6, net.inet.ip.fastforwarding=1


Box A ------Box B (with dual Intel NIC) ----- Box C

Box A is generating packets routed through firewall Box B towards Box 
C. They are connected together with 2 cross over cables.





>Oh, and try increasing your processing limit to 200 and see
>what effect that has.


I will try that next.

         ---Mike