10 gigabit Ethernet - Add on question

[Matthias Saou]

Kuba Ober wrote :

> On Monday 31 December 2007, Robert D. Holtz - Lists wrote:
> > How do you topple the memory bus/cup/peripheral bus restraints to even push
> > past ~2gbps per host, in a practical host environment?
> 
> 1gbps is AFAIK less than 100 megabytes/s if you factor in overheads.
> 
> So 10 gbps is say 800 megabytes/s, practically, at a high link utilization. It 
> should be relatively easy to achieve that on modern hardware. The memory 
> bandwidths are a few times beyond that, same goes for DMA bandwidths. With 
> current PCI Express-supporting chipsets, if you do memory-to-network 
> transfers (just for benchmarking), the other bus devices won't even notice, 
> and all the CPU will see is less leftover memory bandwidth.
> 
> One DDR2 PC-3200 memory stick will happily transfer way more than 1GB/s to 4 
> PCIe lanes, on relatively standard hardware. I tried.

This is true for "raw" network traffic, because limits quickly depend
on what and how you transfer. My testings on some brand new dual quad
core PE1950 III servers (E5410 @ 2.33GHz w/ 6MB cache) show for
instance that an rsync/ssh transfer from one to the other maxes out at
50MB/s because that corresponds to one ssh process taking 100% of one
of the 8 cores. This is one of those cases where pure MHz power
would be more useful than having so many cores :-)

Matthias

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