Hi, There's bus limits on how much data you can push over a PCI bus. You can look around online to see what 32/64 bit, 33/66MHz PCI throughput estimates are.
It changes massively if you use small versus large frames as well. The last time I tried it i couldn't hit gige on PCI; I only managed to get to around 350mbit doing TCP tests. -adrian On 26 August 2013 00:06, Harald Schmalzbauer <h.schmalzba...@omnilan.de>wrote: > Hello, > > I recycled an older box and put an i350-2 together with a second 82541GI > (PCI-slot, one already on-board) into it. > The two i350-ports are used with VMDq for ESXi5.1. > The two 82541GI are used as lagg-nics by a 9.2-RC (amd64) guest as > passthrou PCI device. > Always had good results with such setups, but found out, that nics which > use the legacy driver part of if_em max out at ~0.6Gbits/s (1500 MTU). > > There's another NIC on board of this recycle-box, a 82566-PHY (ICH9 > integrated MAC). > This one uses also if_em, but not legacy code, it reports version 7.3.8 > (compared to 1.0.6). > And it has no problem fully saturating GbE (~925Mbits/s, no jumbo Frames > support anyways). > > I'm using iperf, with and without lagg (doesn't change anyhing, like it > doesn't influence tests on some other boxes with 82576 and i350 (igb)) > I see enough idle cycles so CPU shouldn't limit the legacy if_em nics. > Also, I see the 82541 consuming arround 8k irqs. Same does the > 82566-PHY, but with much higher throughput... > > I'd like to know if I can't generally expect to saturate older (PCI) GbE > nics the line for any reason... I can remember tigeon cards from more > than a decade ago, which indeed seemd to lack the performance to gain > GbE, but I thought that was no issue shortly later and no "modern" > Intel-GbE card had such constraints!? > Is there any special tuning for legacy if_em (no need for any TCP > tuning, 82566 doesn't have any issue)? > > Thanks, > > -Harry > > _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
