reverted:
--- b/drivers/block/blkpg.c	Thu Jun 26 09:12:14 2003
+++ a/drivers/block/blkpg.c	Thu Jun 26 09:12:14 2003
@@ -261,6 +261,7 @@
 			return blkpg_ioctl(dev, (struct blkpg_ioctl_arg *) arg);
 			
 		case BLKELVGET:
+			blk_print_stats(dev);
 			return blkelvget_ioctl(&blk_get_queue(dev)->elevator,
 					       (blkelv_ioctl_arg_t *) arg);
 		case BLKELVSET:
reverted:
--- b/drivers/block/ll_rw_blk.c	Thu Jun 26 09:12:14 2003
+++ a/drivers/block/ll_rw_blk.c	Thu Jun 26 09:12:14 2003
@@ -490,6 +490,56 @@
 	spin_lock_init(&q->queue_lock);
 }
 
+void blk_print_stats(kdev_t dev) 
+{
+	request_queue_t *q;
+	unsigned long avg_wait;
+	unsigned long min_wait;
+	unsigned long high_wait;
+	unsigned long *d;
+
+	q = blk_get_queue(dev);
+	if (!q)
+		return;
+
+	min_wait = q->min_wait;
+	if (min_wait == ~0UL)
+		min_wait = 0;
+	if (q->num_wait) 
+		avg_wait = q->total_wait / q->num_wait;
+	else
+		avg_wait = 0;
+	printk("device %s: num_req %lu, total jiffies waited %lu\n", 
+	       kdevname(dev), q->num_req, q->total_wait);
+	printk("\t%lu forced to wait\n", q->num_wait);
+	printk("\t%lu min wait, %lu max wait\n", min_wait, q->max_wait);
+	printk("\t%lu average wait\n", avg_wait);
+	d = q->deviation;
+	printk("\t%lu < 100, %lu < 200, %lu < 300, %lu < 400, %lu < 500\n",
+               d[0], d[1], d[2], d[3], d[4]);
+	high_wait = d[0] + d[1] + d[2] + d[3] + d[4];
+	high_wait = q->num_wait - high_wait;
+	printk("\t%lu waits longer than 500 jiffies\n", high_wait);
+}
+
+static void reset_stats(request_queue_t *q)
+{
+	q->max_wait		= 0;
+	q->min_wait		= ~0UL;
+	q->total_wait		= 0;
+	q->num_req		= 0;
+	q->num_wait		= 0;
+	memset(q->deviation, 0, sizeof(q->deviation));
+}
+void blk_reset_stats(kdev_t dev) 
+{
+	request_queue_t *q;
+	q = blk_get_queue(dev);
+	if (!q)
+	    return;
+	printk("reset latency stats on device %s\n", kdevname(dev));
+	reset_stats(q);
+}
 static int __make_request(request_queue_t * q, int rw, struct buffer_head * bh);
 
 /**
@@ -542,6 +592,8 @@
 	q->full			= 0;
 	q->can_throttle		= 0;
 
+	reset_stats(q);
+
 	/*
 	 * These booleans describe the queue properties.  We set the
 	 * default (and most common) values here.  Other drivers can
@@ -647,6 +699,8 @@
 static struct request *__get_request_wait(request_queue_t *q, int rw)
 {
 	register struct request *rq;
+	unsigned long wait_start = jiffies;
+	unsigned long time_waited;
 	DECLARE_WAITQUEUE(wait, current);
 
 	add_wait_queue_exclusive(&q->wait_for_requests, &wait);
@@ -669,6 +723,17 @@
 	if (!waitqueue_active(&q->wait_for_requests))
 		clear_full_and_wake(q);
 
+	time_waited = jiffies - wait_start;
+	if (time_waited > q->max_wait)
+		q->max_wait = time_waited;
+	if (time_waited && time_waited < q->min_wait)
+		q->min_wait = time_waited;
+	q->total_wait += time_waited;
+	q->num_wait++;
+	if (time_waited < 500) {
+		q->deviation[time_waited/100]++;
+	}
+
 	return rq;
 }
 
@@ -1157,6 +1222,7 @@
 	req->rq_dev = bh->b_rdev;
 	req->start_time = jiffies;
 	req_new_io(req, 0, count);
+	q->num_req++;
 	blk_started_io(count);
 	blk_started_sectors(req, count);
 	add_request(q, req, insert_here);
reverted:
--- b/fs/super.c	Thu Jun 26 09:12:14 2003
+++ a/fs/super.c	Thu Jun 26 09:12:14 2003
@@ -726,6 +726,7 @@
 	if (!fs_type->read_super(s, data, flags & MS_VERBOSE ? 1 : 0))
 		goto Einval;
 	s->s_flags |= MS_ACTIVE;
+	blk_reset_stats(dev);
 	path_release(&nd);
 	return s;
 
reverted:
--- b/include/linux/blkdev.h	Thu Jun 26 09:12:14 2003
+++ a/include/linux/blkdev.h	Thu Jun 26 09:12:14 2003
@@ -162,8 +162,17 @@
 	 * Tasks wait here for free read and write requests
 	 */
 	wait_queue_head_t	wait_for_requests;
+	unsigned long           max_wait;
+	unsigned long           min_wait;
+	unsigned long           total_wait;
+	unsigned long           num_req;
+	unsigned long           num_wait;
+	unsigned long           deviation[5];
 };
 
+void blk_reset_stats(kdev_t dev);
+void blk_print_stats(kdev_t dev);
+
 #define blk_queue_plugged(q)	(q)->plugged
 #define blk_fs_request(rq)	((rq)->cmd == READ || (rq)->cmd == WRITE)
 #define blk_queue_empty(q)	list_empty(&(q)->queue_head)
@@ -269,7 +278,7 @@
 
 #define MAX_SEGMENTS 128
 #define MAX_SECTORS 255
+#define MAX_QUEUE_SECTORS (2 << (20 - 9)) /* 4 mbytes when full sized */
-#define MAX_QUEUE_SECTORS (2 << (20 - 9)) /* 2 mbytes when full sized */
 #define MAX_NR_REQUESTS 1024 /* 1024k when in 512 units, normally min is 1M in 1k units */
 
 #define PageAlignSize(size) (((size) + PAGE_SIZE -1) & PAGE_MASK)