Add uma_set_align() interface, which will be called at most once during

boot by MD code to indicated detected alignment preference.  Rather than
cache alignment being encoded in UMA consumers by defining a global
alignment value of (16 - 1) in UMA_ALIGN_CACHE, UMA_ALIGN_CACHE is now
a special value (-1) that causes UMA to look at registered alignment.  If
no preferred alignment has been selected by MD code, a default alignment
of (16 - 1) will be used.

Currently, no hardware platforms specify alignment; architecture
maintainers will need to modify MD startup code to specify an alignment
if desired.  This must occur before initialization of UMA so that all UMA
zones pick up the requested alignment.

Reviewed by:	jeff, alc
Submitted by:	attilio

2 files changed, 26 insertions, 2 deletions

diff --git a/sys/vm/uma.h b/sys/vm/uma.h
index 0027177..c082e96 100644
--- a/sys/vm/uma.h
+++ b/sys/vm/uma.h
@@ -236,7 +236,7 @@ uma_zone_t uma_zsecond_create(char *name, uma_ctor ctor, uma_dtor dtor,
 #define UMA_ALIGN_INT	(sizeof(int) - 1)	/* "" int */
 #define UMA_ALIGN_SHORT	(sizeof(short) - 1)	/* "" short */
 #define UMA_ALIGN_CHAR	(sizeof(char) - 1)	/* "" char */
-#define UMA_ALIGN_CACHE	(16 - 1)		/* Cache line size align */
+#define UMA_ALIGN_CACHE	(0 - 1)			/* Cache line size align */
 
 /*
  * Destroys an empty uma zone.  If the zone is not empty uma complains loudly.
@@ -388,6 +388,18 @@ void uma_startup2(void);
 void uma_reclaim(void);
 
 /*
+ * Sets the alignment mask to be used for all zones requesting cache
+ * alignment.  Should be called by MD boot code prior to starting VM/UMA.
+ *
+ * Arguments:
+ *	align The alignment mask
+ *
+ * Returns:
+ *	Nothing
+ */
+void uma_set_align(int align);
+
+/*
  * Switches the backing object of a zone
  *
  * Arguments:
diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index fa2cb05..eb00bfe 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -111,6 +111,9 @@ static uma_zone_t slabrefzone;	/* With refcounters (for UMA_ZONE_REFCNT) */
  */
 static uma_zone_t hashzone;
 
+/* The boot-time adjusted value for cache line alignment. */
+static int uma_align_cache = 16 - 1;
+
 static MALLOC_DEFINE(M_UMAHASH, "UMAHash", "UMA Hash Buckets");
 
 /*
@@ -1707,13 +1710,22 @@ uma_kcreate(uma_zone_t zone, size_t size, uma_init uminit, uma_fini fini,
 	args.size = size;
 	args.uminit = uminit;
 	args.fini = fini;
-	args.align = align;
+	args.align = (align == UMA_ALIGN_CACHE) ? uma_align_cache : align;
 	args.flags = flags;
 	args.zone = zone;
 	return (uma_zalloc_internal(kegs, &args, M_WAITOK));
 }
 
 /* See uma.h */
+void
+uma_set_align(int align)
+{
+
+	if (align != UMA_ALIGN_CACHE)
+		uma_align_cache = align;
+}
+
+/* See uma.h */
 uma_zone_t
 uma_zcreate(char *name, size_t size, uma_ctor ctor, uma_dtor dtor,
 		uma_init uminit, uma_fini fini, int align, u_int32_t flags)