Following a clean install of Ubuntu 10.10 on my desktop machine (the one with Nvidia GeForce GT220), I’ve noticed some weird entries in dmsg: NVRM: os_raise_smp_barrier(). What this translated to was some weird “hang-ups”..which got more and more annoying. Apparently it has something to do with the PowerMizer mode in the NVIDIA X Server Settings. By default it is set to “Adaptive”, so after changing it to “Prefer Maximum Performance” everything got back to normal!

To conclude, in order to fix NVRM: os_raise_smp_barrier(), all you have to do is to switch from Adaptive to Prefer Maximum Performance in the PowerMizer section of the NVIDIA X Server Settings, which you can reach by clicking on System -> Administration -> NVIDIA X Server Settings -> PowerMizer (near the bottom of the list).

To make changes permanent, you will have to edit your /etc/X11/xorg.conf file, and add the line in bold to the device section specific to your video card driver:

Section "Device"
        Identifier      "Default Device"
        Option "RegistryDwords" "PowerMizerEnable=0x1; PerfLevelSrc=0x2222; PowerMizerLevel=0x1; PowerMizerDefault=0x1; PowerMizerDefaultAC=0x1"
        Driver  "nvidia"
        Option  "NoLogo"        "True"
EndSection

I hope this helps!

Andrei