If you're running a kernel built with my vnode_pager_sync changes (revision
1.23 of vnode_pager.c, of 1997/02/13 02:54:11) you should update to the
current revision.  Revision 1.23 contained two serious bugs:

        * It did not lock the VM object associated with the vnode.  You are
          much less likely to have seen this than
        * It (incorrectly) removed pages from the paging queues, which caused
          the VM system to lose track of memory.  Depending how much memory
          your machine has, this could lead to excessive paging, the commonly
          reported symptom, or eventual deadlock.

Credit goes to Charles Hannum for figuring this out.

A fix for these problems has been committed and will appear in tonight's SUP.

I apologize for any inconvenience which this has caused.

Thor