On Thu, Feb 18, 2010 at 07:32:48AM -0800, Patrick Mahan wrote: > All, > > I have seen a few mentions on the mailing lists in regard to issues > with em(4) and FreeBSD 8.0 with regard to throughput. > > We are also seeing similar issues on HP Proliant systems with > this HP GE interfaces. Previously we were running FreeBSD 6.2 and > iperf was showing ~900 Mbits/sec between two directly connected > systems. After the upgrade, iperf only shows around ~350 Mbits/sec. > > This seems only to be happening on the HP's. When we upgrade another > x86 box (privately built) we are seeing ~900 Mbits/sec even to > one of the HP systems. > > I haven't seen anything yet to account for this behavior. Has anyone > else seen similar issues? >
I know there is a possible Tx checksum offloading issue but testing with iperf may not hit the case. One of the big change made in 8.x is switching to buf_ring which will take advantage of multi TX queues. So the only guess I have is TCP segment reordering caused by em(4) and buf_ring interface. Can you capture the traffic on receiver side and check whether you see out-of-ordered TCP segment delivery? If the theory is right you may see the lots of out-of-ordered segments(this could be easily checked on receiver side with netstat -s after clearing the stats) and it will be more frequently seen when TCP window scaling is used. Personally I had trouble to reproduce it on my environments. It may depend on specific workloads. > Thanks, > > Patrick _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
