[Beowulf] Re: typical latencies for gigabit ethernet

Dave Love d.love at liverpool.ac.uk
Mon Jun 29 14:55:25 PDT 2009

Scott Atchley <atchley at myri.com> writes:

> 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.).

I can't remember if I tried it, but it's documented to be adjustable in
the range 100-100000 interrupts/s.

> Your results may be specific to that driver.

Sure.  The only ones I have access to which are tunable with ethtool are
the two Broadcoms for which I posted the data.

> I have head that some Ethernet drivers do or will support adaptive  
> coalescing which may give better performance than manually tuning and  
> without modifying the NIC firmware for OMX.

As I said, not in the case of the ones I tried (even in the low-latency
adaptive mode which the e1000 doc says to use for HPC).

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