Index: sys/kern/subr_blist.c
===================================================================
--- sys/kern/subr_blist.c
+++ sys/kern/subr_blist.c
@@ -295,7 +295,7 @@
  *		     not be allocated.
  */
 daddr_t
-blist_alloc(blist_t bl, int *count, int maxcount)
+blist_alloc(blist_t bl, daddr_t *io_cursor, int *count, int maxcount)
 {
 	daddr_t blk, cursor;
 
@@ -310,14 +310,14 @@
 	 * non-zero.  When the cursor is zero, an allocation failure will
 	 * stop further iterations.
 	 */
-	for (cursor = bl->bl_cursor;; cursor = 0) {
+	for (cursor = *io_cursor;; cursor = 0) {
 		blk = blst_meta_alloc(bl->bl_root, cursor, count, maxcount,
 		    bl->bl_radix);
 		if (blk != SWAPBLK_NONE) {
 			bl->bl_avail -= *count;
-			bl->bl_cursor = blk + *count;
-			if (bl->bl_cursor == bl->bl_blocks)
-				bl->bl_cursor = 0;
+			*io_cursor = blk + *count;
+			if (*io_cursor == bl->bl_blocks)
+				*io_cursor = 0;
 			return (blk);
 		}
 		if (cursor == 0)
@@ -404,8 +404,7 @@
 void
 blist_print(blist_t bl)
 {
-	printf("BLIST avail = %jd, cursor = %08jx {\n",
-	    (uintmax_t)bl->bl_avail, (uintmax_t)bl->bl_cursor);
+	printf("BLIST avail = %jd {\n", (uintmax_t)bl->bl_avail);
 
 	if (bl->bl_root->bm_bitmap != 0)
 		blst_radix_print(bl->bl_root, 0, bl->bl_radix, 4);
Index: sys/sys/blist.h
===================================================================
--- sys/sys/blist.h
+++ sys/sys/blist.h
@@ -81,7 +81,6 @@
 	daddr_t		bl_blocks;	/* area of coverage		*/
 	daddr_t		bl_avail;	/* # available blocks		*/
 	u_daddr_t	bl_radix;	/* coverage radix		*/
-	daddr_t		bl_cursor;	/* next-fit search starts at	*/
 	blmeta_t	bl_root[1];	/* root of radix tree		*/
 } *blist_t;
 
@@ -92,7 +91,7 @@
 
 struct sbuf;
 
-daddr_t	blist_alloc(blist_t blist, int *count, int maxcount);
+daddr_t	blist_alloc(blist_t blist, daddr_t *cursor, int *count, int maxcount);
 daddr_t	blist_avail(blist_t blist);
 blist_t	blist_create(daddr_t blocks, int flags);
 void	blist_destroy(blist_t blist);
Index: sys/vm/swap_pager.h
===================================================================
--- sys/vm/swap_pager.h
+++ sys/vm/swap_pager.h
@@ -65,6 +65,7 @@
 	swblk_t	sw_first;
 	swblk_t	sw_end;
 	struct blist *sw_blist;
+	daddr_t	sw_cursor;	/* next-fit search starts at	*/
 	TAILQ_ENTRY(swdevt)	sw_list;
 	sw_strategy_t		*sw_strategy;
 	sw_close_t		*sw_close;
Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c
+++ sys/vm/swap_pager.c
@@ -702,6 +702,53 @@
 	object->type = OBJT_DEAD;
 }
 
+static void
+swapdev_trim(struct swdevt *sp)
+{
+	struct stat sb;
+	daddr_t blk;
+	const char *devname;
+	u_long nblks;
+	off_t ioarg[2];
+	int fd, npages, mpages;
+
+	/* Give up if there's no filename. */
+	if (!vn_isdisk(sp->sw_vp, NULL))
+		return;
+
+	/* Quit if the cursor is too far behind the trimmer. */
+	nblks = sp->sw_nblks;
+	npages = sp->sw_trimmer + nblks - sp->sw_cursor;
+	if (npages % nblks >= nblks / 5)
+		return;
+
+	/* Grab a lot of free space allocated long ago. */
+	npages = 1;
+	mpages = 10000;
+	blk = blist_alloc(sp->sw_blist, &sp->sw_trimmer, &npages, mpages);
+
+	/* Quit if there's nothing free between the trimmer and cursor. */
+	if (blk == SWAPBLK_NONE)
+		return;
+	if ((blk + nblks - sp->sw_cursor) % nblks > nblks / 5) {
+		/* The trim allocation jumped the cursor. Bail out. */
+		blist_free(sp->sw_blist, blk, npages);
+		return;
+	}
+	blk += sp->sw_first;
+	devname = devtoname(sp->sw_vp->v_rdev);
+	fd = open(devname, O_WRONLY);
+	if (fd < 0)
+		errx(1, "Cannot open %s", name);
+	ioarg[0] = blk;
+	ioarg[1] = npages;
+	if (ioctl(fd, DIOCGDELETE, ioarg) != 0)
+		warn("ioctl(DIOCGDELETE)");
+	close(fd);
+	bl -= sp->sw_first;
+	blist_free(sp->sw_blist, blk, npages);
+}
+
 /************************************************************************
  *			SWAP PAGER BITMAP ROUTINES			*
  ************************************************************************/
@@ -737,7 +784,8 @@
 		if (sp == NULL)
 			sp = TAILQ_FIRST(&swtailq);
 		if ((sp->sw_flags & SW_CLOSING) == 0)
-			blk = blist_alloc(sp->sw_blist, &npages, mpages);
+			blk = blist_alloc(sp->sw_blist, &sp->sw_cursor,
+			    &npages, mpages);
 		if (blk != SWAPBLK_NONE)
 			break;
 		sp = TAILQ_NEXT(sp, sw_list);
@@ -753,6 +801,7 @@
 		blk += sp->sw_first;
 		sp->sw_used += npages;
 		swap_pager_avail -= npages;
+		swapdev_trim(sp);
 		swp_sizecheck();
 		swdevhd = TAILQ_NEXT(sp, sw_list);
 	} else {
@@ -2310,6 +2359,8 @@
 	sp->sw_flags = flags;
 
 	sp->sw_blist = blist_create(nblks, M_WAITOK);
+	sp->sw_cursor = 0;
+	sp->sw_trimmer = 0;
 	/*
 	 * Do not free the first two block in order to avoid overwriting
 	 * any bsd label at the front of the partition