AW: NAMD 2.9b2-cuda does not scale well compared to NAMD 2.8

From: Norman Geist (
Date: Tue Apr 03 2012 - 02:10:08 CDT

Hi Thomas,

Just for completion, you also didn't mention if you have used ibverbs in
your self compiled cuda build, too. If not, you are possibly using the ipoib
device ib0 (see ifconfig), but that is bad with the default settings. If you
have this ipoib device ib0, check the settings of mode and mtu

cat /sys/class/net/ib0/mode
cat /sys/class/net/ib0/mtu

if datagram and 2440(or similar) appear, change it to (as root)

echo "connected" /sys/class/net/ib0/mode
echo "65520" /sys/class/net/ib0/mtu

And see if the non ibverbs build run better now.

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