I’m surprise given that QNX doesn’t support jumbo frame. Smaller packet would seems to indicate more waisted bandwidth.
Tim, isn’t this kind of waisted time? You need to achieve close or little above 100Mbits right? First playing that close to theoretical limit isn’t ideal. Second why even bother, 1G card are cheap, so is cable, maybe the switch cost a more. So what’s the point of doing all this testing/evaluation if you are sure 1G would take care of the issue.
My only concern would be that if you transfer lots of data in burst, the CPU at the receiving end will also burst while dealing with the incoming data. During that burst there is less CPU to deal with other tasks. Selecting the right priority could take care of that to some extent (you don’t want to miss packet or endup having the stack resend the data either).
Mario,
In truth if we are using 1 Mbit of bandwidth in our final application I’ll be surprised.
However what the architecture will be is 2 machines on the surface and 2 machines subsea on a remotely operated vehicle. They will be seperated by about 4000 metres. In between will be a fibre optic Mux to relay the ethernet data.
There is a cost difference between a 100 Mbit Fibre Optic Mux and 1 Gig Fibre Mux. Plus that Mux bandwidth will be shared with a few other sensor devices. So I was trying to get a rough idea of how much bandwidth we could consume in a worst case and if we should go Gig or 100 Meg on the Mux (I believe we are going Gig). So the test was more from a theoretical standpoint than a practical one and it’s not like I needed to write any code to do it.
Tim
Well I wouldn’t be so sure. QNX 4 used to allocate 1/4 of the systems memory by default. I don’t now what QNX 6 does. Say you have a 512 Meg machine, and the Cache has 128Meg, and you want to send a 256Meg file. Also say, the disk write speed is half the wire speed. By the time the cache fills up, the entire file will have been sent. Again, this is not the most important issue here.
For QNX4 it’s 1/8 not 1/4. Under QNX6 I don’t know ( i changed the cache size on my machine so I can’t tell)