[Beowulf] Re: typical latencies for gigabit ethernet
atchley at myri.com
Mon Jun 29 11:04:50 PDT 2009
On Jun 29, 2009, at 1:44 PM, Scott Atchley wrote:
>> Right, and that's what I did before, with sensible results I thought.
>> Repeating it now on Centos 5.2 and OpenSuSE 10.3, it doesn't behave
>> sensibly, and I don't know what's different from the previous SuSE
>> results apart, probably, from the minor kernel version. If I set
>> rx-frames=0, I see this:
>> rx-usec latency (µs)
>> 20 34.6
>> 12 26.3
>> 6 20.0
>> 1 14.8
>> whereas if I just set rx-frames=1, I get 14.7 µs, roughly
>> of rx-usec. (Those figures are probably ±∼0.2µs.)
> That is odd. I have only tested with Intel e1000 and our myri10ge
> Ethernet driver. The Intel driver does not let you specify value
> other than certain settings (0, 25, etc.). The myri10ge driver does
> allow you to specify any value.
> Your results may be specific to that driver.
As Patrick kindly pointed out, you are using rx-frames and not rx-
usec. They are not equivalent.
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