diff -u -ur linux-2.4.20/drivers/block/elevator.c linux-iosched-1d/drivers/block/elevator.c
--- linux-2.4.20/drivers/block/elevator.c	2003-04-14 14:47:22.000000000 -0400
+++ linux-iosched-1d/drivers/block/elevator.c	2003-04-17 12:15:10.000000000 -0400
@@ -74,6 +74,86 @@
 	return 0;
 }
 
+int elevator_neil_merge(request_queue_t *q, struct request **req,
+			 struct list_head * head,
+			 struct buffer_head *bh, int rw,
+			 int max_sectors)
+{
+	struct list_head *entry = &q->queue_head;
+	unsigned int count = bh->b_size >> 9, ret = ELEVATOR_NO_MERGE;
+	unsigned long read_sectors = 0, write_sectors = 0;
+	unsigned int expire_time = jiffies - 1*HZ;
+	struct request *__rq;
+
+	while ((entry = entry->prev) != head) {
+		__rq = blkdev_entry_to_request(entry);
+
+		/*
+		 * we can't insert beyond a zero sequence point
+		 */
+		if (__rq->elevator_sequence == 0) {
+			goto append;
+		}
+
+		if (__rq->cmd == READ)
+			read_sectors += __rq->nr_sectors;
+		else
+			write_sectors += __rq->nr_sectors;
+
+		if (__rq->rq_dev != bh->b_rdev)
+			continue;
+
+		if (__rq->waiting)
+			continue;
+
+		if (__rq->cmd != rw)
+			continue;
+
+		if (time_before(__rq->start_time, expire_time)) {
+			break;
+		}
+
+		if (__rq->sector + __rq->nr_sectors == bh->b_rsector) {
+			if (__rq->nr_sectors + count <= max_sectors)
+				ret = ELEVATOR_BACK_MERGE;
+			*req = __rq;
+			break;
+		} else if (__rq->sector - count == bh->b_rsector) {
+			if (__rq->nr_sectors + count <= max_sectors)
+				ret = ELEVATOR_FRONT_MERGE;
+			*req = __rq;
+			break;
+		}
+	}
+
+	if (!*req && rw == READ) {
+		long extra_writes = write_sectors - read_sectors;
+		/*
+		 * If there are more writes than reads in the queue then put
+		 * read requests ahead of the extra writes.  This prevents
+		 * writes from starving reads.
+		 */
+		entry = q->queue_head.prev;
+		while (extra_writes > 0 && entry != head) {
+			__rq = blkdev_entry_to_request(entry);
+			if (__rq->cmd == WRITE)
+				extra_writes -= __rq->nr_sectors;
+			entry = entry->prev;
+		}
+		*req = blkdev_entry_to_request(entry);
+	}
+
+append:
+
+	return ret;
+}
+
+void elevator_neil_merge_req(struct request *req, struct request *next)
+{
+	if (time_before(next->start_time, req->start_time))
+		req->start_time = next->start_time;
+}
+
 
 int elevator_linus_merge(request_queue_t *q, struct request **req,
 			 struct list_head * head,
diff -u -ur linux-2.4.20/drivers/block/ll_rw_blk.c linux-iosched-1d/drivers/block/ll_rw_blk.c
--- linux-2.4.20/drivers/block/ll_rw_blk.c	2003-04-14 14:47:22.000000000 -0400
+++ linux-iosched-1d/drivers/block/ll_rw_blk.c	2003-04-17 12:21:59.000000000 -0400
@@ -480,7 +480,7 @@
 void blk_init_queue(request_queue_t * q, request_fn_proc * rfn)
 {
 	INIT_LIST_HEAD(&q->queue_head);
-	elevator_init(&q->elevator, ELEVATOR_LINUS);
+	elevator_init(&q->elevator, ELEVATOR_NEIL);
 	blk_init_free_list(q);
 	q->request_fn     	= rfn;
 	q->back_merge_fn       	= ll_back_merge_fn;
@@ -922,7 +922,8 @@
 			rw = READ;	/* drop into READ */
 		case READ:
 		case WRITE:
-			latency = elevator_request_latency(elevator, rw);
+			/* latency = elevator_request_latency(elevator, rw); */
+			latency = 1;
 			break;
 		default:
 			BUG();
diff -u -ur linux-2.4.20/include/linux/elevator.h linux-iosched-1d/include/linux/elevator.h
--- linux-2.4.20/include/linux/elevator.h	2003-04-14 14:47:24.000000000 -0400
+++ linux-iosched-1d/include/linux/elevator.h	2003-04-15 10:17:23.000000000 -0400
@@ -31,6 +31,9 @@
 void elevator_linus_merge_cleanup(request_queue_t *, struct request *, int);
 void elevator_linus_merge_req(struct request *, struct request *);
 
+int elevator_neil_merge(request_queue_t *, struct request **, struct list_head *, struct buffer_head *, int, int);
+void elevator_neil_merge_req(struct request *, struct request *);
+
 typedef struct blkelv_ioctl_arg_s {
 	int queue_ID;
 	int read_latency;
@@ -101,3 +104,12 @@
 	})
 
 #endif
+
+#define ELEVATOR_NEIL							\
+((elevator_t) {								\
+	0,				/* read_latency */		\
+	0,				/* write_latency */		\
+									\
+	elevator_neil_merge,		/* elevator_merge_fn */		\
+	elevator_neil_merge_req,	/* elevator_merge_req_fn */	\
+	})
Only in linux-iosched-1d: inst.sh