Why does GFS become so slow when the filesystem is close to 100% full?

A GFS filesystem is split up in several resource groups (RGs). The number of resource groups depends on how big the filesystem is, you can check the number by doing a gfs_tool df <mountpoint>

What probably is causing the slowdown is that somebody is trying to create files. The sequence of lock operations to do this is:

1. Acquire an exclusive lock on the...