em0 performance subpar

[Adam Stylinski]

On Thu, Apr 28, 2011 at 03:25:53PM +0100, Steven Hartland wrote:
> * What's your traffic like? e.g. http, large tcp files, tiny udp etc...
> * Is it all on a local switch, if so what switch?
> * Is flow control enabled?
> * Are you seeing high interrupts?
> * Are you disk bound?
> * Are you memory bound?
> * Are you cpu bound?
> 
> Some basic settings we have here:-
> net.inet.tcp.inflight.enable=0
> net.inet.tcp.sendspace=65536
> kern.ipc.nmbclusters=262144
> kern.ipc.maxsockets=204800
> net.inet.tcp.msl=20000
> kern.ipc.maxsockbuf=524288
> net.inet.tcp.sendbuf_max=16777216
> net.inet.tcp.recvbuf_max=16777216
> 
> Note: Large values for kern.ipc.maxsockbuf can hurt performance under
> 8.x but work well under 7.x (never got to the bottom of that)
> 
>     Regards
>     Steve
> 
> 
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I was using the default value for maxsockbuf, doesn't seem to hurt or help.  The only value you've listed that I didn't have tweaked to a comparable value already was the nmbclusters, changing it seems to have no effect, though.  vmstat -i should display my interrupts, which I don't think are particularly high.  I am most definitely not CPU bound (utilization shows no hot CPUs), I have 16GB of memory and plenty allocated to the kernel, and I believe flow control is enabled (should it not be?):
net.inet.flowtable.enable: 1

It's a 16 port netgear gigabit prosafe switch, and it's not likely to be the problem (like I said, the Linux hosts have no issues with the same card).   

-- 
Adam Stylinski
PGP Key: http://pohl.ececs.uc.edu/~adam/publickey.pub
Blog: http://technicallyliving.blogspot.com
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