Index: sys/kern/subr_disk.c
===================================================================
--- sys/kern/subr_disk.c
+++ sys/kern/subr_disk.c
@@ -21,8 +21,13 @@
 #include <sys/bio.h>
 #include <sys/conf.h>
 #include <sys/disk.h>
+#include <sys/sysctl.h>
 #include <geom/geom_disk.h>
 
+static int bioq_batchsize = 128;
+SYSCTL_INT(_debug, OID_AUTO, bioq_batchsize, CTLFLAG_RW,
+    &bioq_batchsize, 0, "BIOQ batch size");
+
 /*-
  * Disk error is the preface to plaintive error messages
  * about failing disk transfers.  It prints messages of the form
@@ -150,6 +155,7 @@
 	TAILQ_INIT(&head->queue);
 	head->last_offset = 0;
 	head->insert_point = NULL;
+	head->batched = 0;
 }
 
 void
@@ -188,6 +194,7 @@
 {
 
 	TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue);
+	head->batched = 0;
 	head->insert_point = bp;
 	head->last_offset = bp->bio_offset;
 }
@@ -246,6 +253,16 @@
 		return;
 	}
 
+	/*
+	 * Impose a maximum number of passengers in any given
+	 * elevator car. This limits the maximum latency for any
+	 * given request without signficantly affecting the average.
+	 */
+	if (bioq_batchsize > 0 && head->batched > bioq_batchsize) {
+		bioq_insert_tail(head, bp);
+		return;
+	}
+
 	prev = NULL;
 	key = bioq_bio_key(head, bp);
 	cur = TAILQ_FIRST(&head->queue);
@@ -264,4 +281,6 @@
 		TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
 	else
 		TAILQ_INSERT_AFTER(&head->queue, prev, bp, bio_queue);
+
+	head->batched++;
 }
Index: sys/sys/bio.h
===================================================================
--- sys/sys/bio.h
+++ sys/sys/bio.h
@@ -129,6 +129,7 @@
 	TAILQ_HEAD(bio_queue, bio) queue;
 	off_t last_offset;
 	struct	bio *insert_point;
+	int batched;
 };
 
 extern struct vm_map *bio_transient_map;