Hello, Bridging between two interfaces is NOT something that is going to benefit from having multiple CPUs. There are too many synchronisation points, the receiving NIC, the sending NIC, the ethernet address database, etc.
In other words, comparing the amount of 'work' it needs to handle a packet (tell the network card to receive it, lookup the ethernet address and sent it back out again), the cost of synchronising the work of the multiple processors is much higher. cheers, Lennert On Fri, Jan 03, 2003 at 12:21:28PM -0800, me athome wrote: > Hello, > > I am testing linux bridging with kernel 2.4.20 on a > dual P4 2.4 GHz Xeon and found problematic results. > With a packet size of 128Bytes the maximum throughput > is about 160Mbps (Full duplex). I than tried the same > test with only one P4 and the throughput was the same. > That leads me to believe that the second CPU was not > doing anything during the first test (and indeed the > system and use utilization was always 0%). > > At this point I was convinced that the bridge code > cannot use the second cpu so I tried the whole setup > on my dual P3 and on that machine there is a big > difference between one and two cpus enabled. > > I went back to the dual P4 and tried the clean 2.4.20 > kernel with Ingo?s irq balance patch > (irqbalance-2.4.20-MRC.patch.txt). The result was the > same although the interrupts were indeed balanced. The > behavior of ?top? was much different though, before > after 160Mbps cpu0 would be in 100% system and cpu1 > was always 0% while now both cpu0 and cpu1 were at 50% > (and no more). > > I tried every combination of hyper treading on/off > with or without the irqbalance patch as well as > acpismp=force. > > Am I crazy for expecting the second P4 to do > something? > > Ron. > > > > > > > __________________________________________________ > Do you Yahoo!? > Yahoo! Mail Plus - Powerful. Affordable. Sign up now. > http://mailplus.yahoo.com > _______________________________________________ > Bridge mailing list > [EMAIL PROTECTED] > http://www.math.leidenuniv.nl/mailman/listinfo/bridge > _______________________________________________ Bridge mailing list [EMAIL PROTECTED] http://www.math.leidenuniv.nl/mailman/listinfo/bridge
