[packages/kernel.git] / linux-2.4.20-new_IO_scheduler.patch

diff -u -ur linux-2.4.20/drivers/block/elevator.c linux-iosched-2/drivers/block/elevator.c
--- linux-2.4.20/drivers/block/elevator.c	2003-04-14 14:47:22.000000000 -0400
+++ linux-iosched-2/drivers/block/elevator.c	2003-05-30 17:28:57.000000000 -0400
@@ -74,6 +74,81 @@
 	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;
+	struct request *__rq;
+	unsigned int count = bh->b_size >> 9, ret = ELEVATOR_NO_MERGE;
+	unsigned int reads = 0, writes = 0;
+	/* XXX make tunable? */
+	unsigned int expire_time = jiffies - 1*HZ;
+
+	if (list_empty(&q->queue_head))
+		goto out;
+
+	/* try to merge requests, fall back to ordering them by sector */
+	while ((entry = entry->prev) != head) {
+		__rq = blkdev_entry_to_request(entry);
+
+		if (__rq->elevator_sequence <= 0)
+			break;
+		if (__rq->cmd == READ)
+			++reads;
+		else
+			++writes;
+		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 (bh->b_rsector > __rq->sector)
+			*req = __rq;
+		if (__rq->nr_sectors + count > max_sectors)
+			continue;
+		if (__rq->sector + __rq->nr_sectors == bh->b_rsector) {
+			ret = ELEVATOR_BACK_MERGE;
+			*req = __rq;
+			goto out;
+		} else if (__rq->sector - count == bh->b_rsector) {
+			ret = ELEVATOR_FRONT_MERGE;
+			*req = __rq;
+			goto out;
+		}
+	}
+	if (!*req && rw == READ) {
+		int extra_writes = writes - reads;
+		/*
+		 * 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;
+			else if (time_before(__rq->start_time, expire_time))
+				break;
+			entry = entry->prev;
+		}
+		*req = blkdev_entry_to_request(entry);
+	}
+out:
+	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-2/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-2/drivers/block/ll_rw_blk.c	2003-05-30 17:27:16.000000000 -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-2/include/linux/elevator.h
--- linux-2.4.20/include/linux/elevator.h	2003-04-14 14:47:24.000000000 -0400
+++ linux-iosched-2/include/linux/elevator.h	2003-05-30 17:27:16.000000000 -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 */	\
+	})
Commit	Line	Data
d362f46d	1	diff -u -ur linux-2.4.20/drivers/block/elevator.c linux-iosched-2/drivers/block/elevator.c
	2	--- linux-2.4.20/drivers/block/elevator.c 2003-04-14 14:47:22.000000000 -0400
	3	+++ linux-iosched-2/drivers/block/elevator.c 2003-05-30 17:28:57.000000000 -0400
	4	@@ -74,6 +74,81 @@
	5	return 0;
	6	}
	7
	8	+int elevator_neil_merge(request_queue_t q, struct request *req,
	9	+ struct list_head * head,
	10	+ struct buffer_head *bh, int rw,
	11	+ int max_sectors)
	12	+{
	13	+ struct list_head *entry = &q->queue_head;
	14	+ struct request *__rq;
	15	+ unsigned int count = bh->b_size >> 9, ret = ELEVATOR_NO_MERGE;
	16	+ unsigned int reads = 0, writes = 0;
	17	+ /* XXX make tunable? */
	18	+ unsigned int expire_time = jiffies - 1*HZ;
	19	+
	20	+ if (list_empty(&q->queue_head))
	21	+ goto out;
	22	+
	23	+ /* try to merge requests, fall back to ordering them by sector */
	24	+ while ((entry = entry->prev) != head) {
	25	+ __rq = blkdev_entry_to_request(entry);
	26	+
	27	+ if (__rq->elevator_sequence <= 0)
	28	+ break;
	29	+ if (__rq->cmd == READ)
	30	+ ++reads;
	31	+ else
	32	+ ++writes;
	33	+ if (__rq->rq_dev != bh->b_rdev)
	34	+ continue;
	35	+ if (__rq->waiting)
	36	+ continue;
	37	+ if (__rq->cmd != rw)
	38	+ continue;
	39	+ if (time_before(__rq->start_time, expire_time))
	40	+ break;
	41	+ if (bh->b_rsector > __rq->sector)
	42	+ *req = __rq;
	43	+ if (__rq->nr_sectors + count > max_sectors)
	44	+ continue;
	45	+ if (__rq->sector + __rq->nr_sectors == bh->b_rsector) {
	46	+ ret = ELEVATOR_BACK_MERGE;
	47	+ *req = __rq;
	48	+ goto out;
	49	+ } else if (__rq->sector - count == bh->b_rsector) {
	50	+ ret = ELEVATOR_FRONT_MERGE;
	51	+ *req = __rq;
	52	+ goto out;
	53	+ }
	54	+ }
	55	+ if (!*req && rw == READ) {
	56	+ int extra_writes = writes - reads;
	57	+ /*
	58	+ * If there are more writes than reads in the queue then put
	59	+ * read requests ahead of the extra writes. This prevents
	60	+ * writes from starving reads.
	61	+ */
	62	+ entry = q->queue_head.prev;
	63	+ while (extra_writes > 0 && entry != head) {
	64	+ __rq = blkdev_entry_to_request(entry);
65	+ if (__rq->cmd == WRITE)
66	+ --extra_writes;
67	+ else if (time_before(__rq->start_time, expire_time))
68	+ break;
69	+ entry = entry->prev;
70	+ }
71	+ *req = blkdev_entry_to_request(entry);
72	+ }
73	+out:
74	+ return ret;
75	+}
76	+
77	+void elevator_neil_merge_req(struct request req, struct request next)
78	+{
79	+ if (time_before(next->start_time, req->start_time))
80	+ req->start_time = next->start_time;
81	+}
82	+
83
84	int elevator_linus_merge(request_queue_t q, struct request *req,
85	struct list_head * head,
86	diff -u -ur linux-2.4.20/drivers/block/ll_rw_blk.c linux-iosched-2/drivers/block/ll_rw_blk.c
87	--- linux-2.4.20/drivers/block/ll_rw_blk.c 2003-04-14 14:47:22.000000000 -0400
88	+++ linux-iosched-2/drivers/block/ll_rw_blk.c 2003-05-30 17:27:16.000000000 -0400
89	@@ -480,7 +480,7 @@
90	void blk_init_queue(request_queue_t * q, request_fn_proc * rfn)
91	{
92	INIT_LIST_HEAD(&q->queue_head);
93	- elevator_init(&q->elevator, ELEVATOR_LINUS);
94	+ elevator_init(&q->elevator, ELEVATOR_NEIL);
95	blk_init_free_list(q);
96	q->request_fn = rfn;
97	q->back_merge_fn = ll_back_merge_fn;
98	@@ -922,7 +922,8 @@
99	rw = READ; /* drop into READ */
100	case READ:
101	case WRITE:
102	- latency = elevator_request_latency(elevator, rw);
103	+ /* latency = elevator_request_latency(elevator, rw); */
104	+ latency = 1;
105	break;
106	default:
107	BUG();
108	diff -u -ur linux-2.4.20/include/linux/elevator.h linux-iosched-2/include/linux/elevator.h
109	--- linux-2.4.20/include/linux/elevator.h 2003-04-14 14:47:24.000000000 -0400
110	+++ linux-iosched-2/include/linux/elevator.h 2003-05-30 17:27:16.000000000 -0400
111	@@ -31,6 +31,9 @@
112	void elevator_linus_merge_cleanup(request_queue_t , struct request , int);
113	void elevator_linus_merge_req(struct request , struct request );
114
115	+int elevator_neil_merge(request_queue_t , struct request , struct list_head , struct buffer_head *, int, int);
116	+void elevator_neil_merge_req(struct request , struct request );
117	+
118	typedef struct blkelv_ioctl_arg_s {
119	int queue_ID;
120	int read_latency;
121	@@ -101,3 +104,12 @@
122	})
123
124	#endif
125	+
126	+#define ELEVATOR_NEIL \
127	+((elevator_t) { \
128	+ 0, /* read_latency */ \
129	+ 0, /* write_latency */ \
130	+ \
131	+ elevator_neil_merge, /* elevator_merge_fn */ \
132	+ elevator_neil_merge_req, /* elevator_merge_req_fn */ \
133	+ })
134