The new fedup process completed my upgrade to Fedora 18 with no issues a couple of months ago. After the normal minor wrangling to get four monitors working again, I immediately began experiencing a more serious issue: persistent oom-killer, typically a few hours after boot and despite plenty of memory.

Oom-killer continued to target various aspects of X, so trying to rule things out, I tried different desktop environments. Unfortunately, it has persisted across XFCE, LXDE, and KDE. All attempts at isolating a single problematic application have come up empty. A decent resource on tracing memory issues like this is, which analysis points to fragmentation, but in my case I seem to be exhausting DMA memory. I created a bug tracking the issue.

vm.panic_on_oom = 1
kernel.panic = 10

I had to resort to the above sysctl.conf, with further mitigation being to reboot at the beginning and end of the day, leaving the system in runlevel 3 when not in use. Barely tolerable. My least successful upgrade.