svn commit: r254229 - head/sys/arm/arm

[Olivier Houchard]

Author: cognet
Date: Sun Aug 11 21:21:02 2013
New Revision: 254229
URL: http://svnweb.freebsd.org/changeset/base/254229

Log:
  Only allocate 2 bounce pages for maps that can only use them for buffers that
  are unaligned on cache lines boundary, as we will never need more.

Modified:
  head/sys/arm/arm/busdma_machdep-v6.c

Modified: head/sys/arm/arm/busdma_machdep-v6.c
==============================================================================
--- head/sys/arm/arm/busdma_machdep-v6.c	Sun Aug 11 21:15:04 2013	(r254228)
+++ head/sys/arm/arm/busdma_machdep-v6.c	Sun Aug 11 21:21:02 2013	(r254229)
@@ -425,6 +425,8 @@ bus_dma_tag_create(bus_dma_tag_t parent,
 	if (_bus_dma_can_bounce(newtag->lowaddr, newtag->highaddr)
 	 || newtag->alignment > 1)
 		newtag->flags |= BUS_DMA_COULD_BOUNCE;
+	else
+		maxsize = 2; /* Need at most 2 bounce pages for unaligned access on cache line boundaries */
 
 	if ((flags & BUS_DMA_ALLOCNOW) != 0) {
 		struct bounce_zone *bz;
@@ -519,7 +521,10 @@ static int allocate_bz_and_pages(bus_dma
 	 * Attempt to add pages to our pool on a per-instance
 	 * basis up to a sane limit.
 	 */
-	maxpages = MAX_BPAGES;
+	if (dmat->flags & BUS_DMA_COULD_BOUNCE)
+		maxpages = MAX_BPAGES;
+	else
+		maxpages = 2 * bz->map_count; /* Only need at most 2 pages for buffers unaligned on cache line boundaries */
 	if ((dmat->flags & BUS_DMA_MIN_ALLOC_COMP) == 0
 	    || (bz->map_count > 0 && bz->total_bpages < maxpages)) {
 		int pages;