Ingo Flaschberger wrote:
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
Nice piece of hardware.
Don't like the 2.5" one disk option though.
And not shure what to think of:
"Seven 10/100/1000Mbps (through PCI-E by one
interface) ports (RJ-45)"
Which seems to suggest everything comes in thru on PCI-E interface.
That than better have 8 or 16 lanes.
Hopefully there will be direct memory bus connected nic's in future.
(HyperTransport connected nic's)
Well that is going to be an AMD only solution, and I'm not even shure
that AMD would like to have other things than CPU's on that bus.
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.
MSI is not used for regular PCI busses.Could be that PCI-E does use it.
I believe youon that. But even than I'd like to know where the
bottleneck is in the 100kp/s limit with 64byte pakkets.
But 100kpps is great for a router hardware of about 600eur.
I've seen routers 10 times that expensive, not able to that.
--WjW
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