Coalesce pipe allocations and frees. Previously, the pipe code

would allocate two 'struct pipe's from the pipe zone, and malloc a
mutex.

- Create a new "struct pipepair" object holding the two 'struct
  pipe' instances, struct mutex, and struct label reference.  Pipe
  structures now have a back-pointer to the pipe pair, and a
  'pipe_present' flag to indicate whether the half has been
  closed.

- Perform mutex init/destroy in zone init/destroy, avoiding
  reallocating the mutex for each pipe.  Perform most pipe structure
  setup in zone constructor.

- VM memory mappings for pageable buffers are still done outside of
  the UMA zone.

- Change MAC API to speak 'struct pipepair' instead of 'struct pipe',
  update many policies.  MAC labels are also handled outside of the
  UMA zone for now.  Label-only policy modules don't have to be
  recompiled, but if a module is recompiled, its pipe entry points
  will need to be updated.  If a module actually reached into the
  pipe structures (unlikely), that would also need to be modified.

These changes substantially simplify failure handling in the pipe
code as there are many fewer possible failure modes.

On half-close, pipes no longer free the 'struct pipe' for the closed
half until a full-close takes place.  However, VM mapped buffers
are still released on half-close.

Some code refactoring is now possible to clean up some of the back
references, etc; this patch attempts not to change the structure
of most of the pipe implementation, only allocation/free code
paths, so as to avoid introducing bugs (hopefully).

This cuts about 8%-9% off the cost of sequential pipe allocation
and free in system call tests on UP and SMP in my micro-benchmarks.
May or may not make a difference in macro-benchmarks, but doing
less work is good.

Reviewed by:	juli, tjr
Testing help:	dwhite, fenestro, scottl, et al

1 files changed, 14 insertions, 3 deletions

diff --git a/sys/sys/pipe.h b/sys/sys/pipe.h
index bdb9104..84464bd 100644
--- a/sys/sys/pipe.h
+++ b/sys/sys/pipe.h
@@ -113,13 +113,24 @@ struct pipe {
 	struct	timespec pipe_ctime;	/* time of status change */
 	struct	sigio *pipe_sigio;	/* information for async I/O */
 	struct	pipe *pipe_peer;	/* link with other direction */
+	struct	pipepair *pipe_pair;	/* container structure pointer */
 	u_int	pipe_state;		/* pipe status info */
 	int	pipe_busy;		/* busy flag, mostly to handle rundown sanely */
-	struct	label *pipe_label;	/* pipe MAC label - shared */
-	struct	mtx *pipe_mtxp;		/* shared mutex between both pipes */
+	int	pipe_present;		/* still present? */
 };
 
-#define PIPE_MTX(pipe)		(pipe)->pipe_mtxp
+/*
+ * Container structure to hold the two pipe endpoints, mutex, and label
+ * pointer.
+ */
+struct pipepair {
+	struct pipe	pp_rpipe;
+	struct pipe	pp_wpipe;
+	struct mtx	pp_mtx;
+	struct label	*pp_label;
+};
+
+#define PIPE_MTX(pipe)		(&(pipe)->pipe_pair->pp_mtx)
 #define PIPE_LOCK(pipe)		mtx_lock(PIPE_MTX(pipe))
 #define PIPE_UNLOCK(pipe)	mtx_unlock(PIPE_MTX(pipe))
 #define PIPE_LOCK_ASSERT(pipe, type)  mtx_assert(PIPE_MTX(pipe), (type))