Unify the 2 concept into a real, minimal, sxlock where the shared
acquisition represent the soft busy and the exclusive acquisition
represent the hard busy.
The old VPO_WANTED mechanism becames the hard-path for this new lock
and it becomes per-page rather than per-object.
The vm_object lock becames an interlock for this functionality:
it can be held in both read or write mode.
However, if the vm_object lock is held in read mode while acquiring
or releasing the busy state, the thread owner cannot make any
assumption on the busy state unless it is also busying it.
Also:
- Add a new flag to directly shared busy pages while vm_page_alloc
and vm_page_grab are being executed. This will be very helpful
once these functions happen under a read object lock.
- Move the swapping sleep into its own per-object flag
The KPI is heavilly changed this is why the version is bumped.
It is very likely that some VM ports users will need to change
their own code.
Sponsored by: EMC / Isilon storage division
Discussed with: alc
Reviewed by: jeff, kib
Tested by: gavin, bapt (older version)
Tested by: pho, scottl
Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.
Reviewed by: ru
Approved by: philip, ed (mentors)
Nuke incorrect usage of .Ar; replace it with .Vt, .Va or .Fa appropriately.
The .Ar mdoc(7) specifier should only be used when displaying command line
arguments.
Approved by: des (mentor)
incomplete and some are just placeholders but I wanted to try to get
something at least into 2.2 on the grounds that what I have is a lot
better than nothing. I also wanted to commit something which documents
the interfaces in 2.2 before I start updating the documentation for 3.0.
This is a definite 2.2 candidate and is also relavent to 2.1 if people
still care about that branch.
