Start implementing queue state updates using fcmpset loops. [2/5]

[markj]

Summary

Introduce vm_page_pqstate_commit(), which is a generic function that
handles more cases than the specialized vm_page_pqstate_commit_*()
functions.

Implement vm_page_mvqueue() (the backend for vm_page_activate(),
vm_page_deactivate(), etc.), vm_page_unwire() and vm_page_release_toq()
using the new pqstate operations. Use vm_page_release_toq() as the
common back-end for vm_page_unwire() and vm_page_release(). This has
the side effect that vm_page_unwire() will leave the page in the active
queue if it is already there.

[jeff]

sys/vm/vm_page.c

3892

As I mentioned elsewhere if there is no object ref and this is the last ref we will requeue the page before calling free below.

Really this should not requeue if old == 1 but only if WIRE_COUNT(old) == 1

[jeff]

Would like to see the last unwire requeue avoided but otherwise LGTM.

[markj]

Committed in r356155.