Firefox has recently been prone to allocating multiple gigabytes of
memory and thrashing my box to death.

I tracked two problems back to gnome-vfs2, which have since been
fixed, but Firefox is still occasionally allocating huge chunks
amounts of memory.

The same update from rawhide which provided the buggy gnome-vfs2 also
came with the version of glibc where getaddrinfo caching was introduced.

I managed to accidentally trigger the bug in Firefox when running in a
debugger, and the only active thread was stopped in __nscd_getai, so I
think it's possible that the problem is in the getaddrinfo caching
changes.

This is on an AMD64 system, which may be related to the problem.