I have a 1.2Ghz Pentium-M appliance, with 4x 32bit, 33MHz pci intel e1000
cards.
With maximum tuning I can "route" ~400mbps with big packets and ~80mbps
with 64byte packets.
around 100kpps, whats not bad for a pci architecture.
To reach higher bandwiths, better busses are needed.
pci-express cards are currently the best choice.
one dedicated pci-express lane (1.25gbps) has more bandwith than a whole
32bit, 33mhz pci-bus.
Like you say routing 400 Mb/s is close to the max of the PCI bus, which
has a theoretical max of 33*4*8 ~ 1Gbps. Now routing is 500Mb/s in, 500Mb/s
out. So you are within 80% of the bus-max, not counting memory-access and
others.
yes.
PCI express will give you a bus per PCI-E device into a central hub, thus
upping the limit to the speed of the FrontSideBus in Intel architectures.
Which at the moment is a lot higher than what a single PCI bus does.
Thats why my next router will be based at this box:
http://www.axiomtek.com/products/ViewProduct.asp?view=429
Hopefully there will be direct memory bus connected nic's in future.
(HyperTransport connected nic's)
What it does not explain is why you can only get 80Mb/s with 64byte packets,
which would suggest other bottlenecks than just the bus.
Perhaps something with interrupts:
http://books.google.at/books?id=pr4fspaQqZkC&pg=PA144&lpg=PA144&dq=pci+interrupt+delay&source=web&ots=zbvVU2CgVx&sig=APe9YjdtK35ccnow7BDI2hzie7s&hl=de#PPA144,M1
MSI (Message-signalled Interrupts) are not very common on PCI
architekture; PCI-E use only MSI.
The kpps keept always around 100, equally if I used fast-forwarding,
fast-interrupts, or higher HZ values than 1000HZ.
But 100kpps is great for a router hardware of about 600eur.
Kind regards,
Ingo Flaschberger
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