From: Nick Piggin <piggin@cyberone.com.au>
Following patch seperates elevator noop, and allows it to be treated
like the other schedulers.
drivers/block/Kconfig.iosched | 21 +++++++++
drivers/block/Makefile | 1
drivers/block/elevator.c | 76 -----------------------------------
drivers/block/ll_rw_blk.c | 13 ++++--
drivers/block/noop-iosched.c | 89 ++++++++++++++++++++++++++++++++++++++++++
5 files changed, 121 insertions(+), 79 deletions(-)
diff -puN drivers/block/elevator.c~standalone-elevator-noop drivers/block/elevator.c
--- 25/drivers/block/elevator.c~standalone-elevator-noop 2003-08-07 15:42:04.000000000 -0700
+++ 25-akpm/drivers/block/elevator.c 2003-08-07 15:42:04.000000000 -0700
@@ -87,72 +87,6 @@ inline int elv_try_last_merge(request_qu
}
/*
- * elevator noop
- *
- * See if we can find a request that this buffer can be coalesced with.
- */
-int elevator_noop_merge(request_queue_t *q, struct list_head **insert,
- struct bio *bio)
-{
- struct list_head *entry = &q->queue_head;
- struct request *__rq;
- int ret;
-
- if ((ret = elv_try_last_merge(q, bio))) {
- *insert = q->last_merge;
- return ret;
- }
-
- while ((entry = entry->prev) != &q->queue_head) {
- __rq = list_entry_rq(entry);
-
- if (__rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER))
- break;
- else if (__rq->flags & REQ_STARTED)
- break;
-
- if (!blk_fs_request(__rq))
- continue;
-
- if ((ret = elv_try_merge(__rq, bio))) {
- *insert = &__rq->queuelist;
- q->last_merge = &__rq->queuelist;
- return ret;
- }
- }
-
- return ELEVATOR_NO_MERGE;
-}
-
-void elevator_noop_merge_requests(request_queue_t *q, struct request *req,
- struct request *next)
-{
- list_del_init(&next->queuelist);
-}
-
-void elevator_noop_add_request(request_queue_t *q, struct request *rq,
- struct list_head *insert_here)
-{
- list_add_tail(&rq->queuelist, &q->queue_head);
-
- /*
- * new merges must not precede this barrier
- */
- if (rq->flags & REQ_HARDBARRIER)
- q->last_merge = NULL;
- else if (!q->last_merge)
- q->last_merge = &rq->queuelist;
-}
-
-struct request *elevator_noop_next_request(request_queue_t *q)
-{
- if (!list_empty(&q->queue_head))
- return list_entry_rq(q->queue_head.next);
-
- return NULL;
-}
-
-/*
* general block -> elevator interface starts here
*/
int elevator_init(request_queue_t *q, elevator_t *type)
@@ -415,18 +349,8 @@ void elv_unregister_queue(struct request
}
}
-elevator_t elevator_noop = {
- .elevator_merge_fn = elevator_noop_merge,
- .elevator_merge_req_fn = elevator_noop_merge_requests,
- .elevator_next_req_fn = elevator_noop_next_request,
- .elevator_add_req_fn = elevator_noop_add_request,
- .elevator_name = "noop",
-};
-
module_init(elevator_global_init);
-EXPORT_SYMBOL(elevator_noop);
-
EXPORT_SYMBOL(elv_add_request);
EXPORT_SYMBOL(__elv_add_request);
EXPORT_SYMBOL(elv_requeue_request);
diff -puN drivers/block/Kconfig.iosched~standalone-elevator-noop drivers/block/Kconfig.iosched
--- 25/drivers/block/Kconfig.iosched~standalone-elevator-noop 2003-08-07 15:42:04.000000000 -0700
+++ 25-akpm/drivers/block/Kconfig.iosched 2003-08-07 15:42:04.000000000 -0700
@@ -1,8 +1,29 @@
+config IOSCHED_NOOP
+ bool "No-op I/O scheduler" if EMBEDDED
+ default y
+ ---help---
+ The no-op I/O scheduler is a minimal scheduler that does basic merging
+ and sorting. Its main uses include non-disk based block devices like
+ memory devices, and specialised software or hardware environments
+ that do their own scheduling and require only minimal assistance from
+ the kernel.
+
config IOSCHED_AS
bool "Anticipatory I/O scheduler" if EMBEDDED
default y
+ ---help---
+ The anticipatory I/O scheduler is the default disk scheduler. It is
+ generally a good choice for most environments, but is quite large and
+ complex when compared to the deadline I/O scheduler, it can also be
+ slower in some cases especially some database loads.
config IOSCHED_DEADLINE
bool "Deadline I/O scheduler" if EMBEDDED
default y
+ ---help---
+ The deadline I/O scheduler is simple and compact, and is often as
+ good as the anticipatory I/O scheduler, and in some database
+ workloads, better. In the case of a single process performing I/O to
+ a disk at any one time, its behaviour is almost identical to the
+ anticipatory I/O scheduler and so is a good choice.
diff -puN drivers/block/ll_rw_blk.c~standalone-elevator-noop drivers/block/ll_rw_blk.c
--- 25/drivers/block/ll_rw_blk.c~standalone-elevator-noop 2003-08-07 15:42:04.000000000 -0700
+++ 25-akpm/drivers/block/ll_rw_blk.c 2003-08-07 15:42:04.000000000 -0700
@@ -1232,11 +1232,14 @@ static elevator_t *chosen_elevator =
&iosched_as;
#elif defined(CONFIG_IOSCHED_DEADLINE)
&iosched_deadline;
-#else
+#elif defined(CONFIG_IOSCHED_NOOP)
&elevator_noop;
+#else
+ NULL;
+#error "You must have at least 1 I/O scheduler selected"
#endif
-#if defined(CONFIG_IOSCHED_AS) || defined(CONFIG_IOSCHED_DEADLINE)
+#if defined(CONFIG_IOSCHED_AS) || defined(CONFIG_IOSCHED_DEADLINE) || defined (CONFIG_IOSCHED_NOOP)
static int __init elevator_setup(char *str)
{
#ifdef CONFIG_IOSCHED_DEADLINE
@@ -1247,11 +1250,15 @@ static int __init elevator_setup(char *s
if (!strcmp(str, "as"))
chosen_elevator = &iosched_as;
#endif
+#ifdef CONFIG_IOSCHED_NOOP
+ if (!strcmp(str, "noop"))
+ chosen_elevator = &elevator_noop;
+#endif
return 1;
}
__setup("elevator=", elevator_setup);
-#endif /* CONFIG_IOSCHED_AS || CONFIG_IOSCHED_DEADLINE */
+#endif /* CONFIG_IOSCHED_AS || CONFIG_IOSCHED_DEADLINE || CONFIG_IOSCHED_NOOP */
request_queue_t *blk_alloc_queue(int gfp_mask)
{
diff -puN drivers/block/Makefile~standalone-elevator-noop drivers/block/Makefile
--- 25/drivers/block/Makefile~standalone-elevator-noop 2003-08-07 15:42:04.000000000 -0700
+++ 25-akpm/drivers/block/Makefile 2003-08-07 15:42:04.000000000 -0700
@@ -15,6 +15,7 @@
obj-y := elevator.o ll_rw_blk.o ioctl.o genhd.o scsi_ioctl.o
+obj-$(CONFIG_IOSCHED_NOOP) += noop-iosched.o
obj-$(CONFIG_IOSCHED_AS) += as-iosched.o
obj-$(CONFIG_IOSCHED_DEADLINE) += deadline-iosched.o
obj-$(CONFIG_MAC_FLOPPY) += swim3.o
diff -puN /dev/null drivers/block/noop-iosched.c
--- /dev/null 2002-08-30 16:31:37.000000000 -0700
+++ 25-akpm/drivers/block/noop-iosched.c 2003-08-07 15:42:04.000000000 -0700
@@ -0,0 +1,89 @@
+/*
+ * elevator noop
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+
+#include <asm/uaccess.h>
+
+/*
+ * See if we can find a request that this buffer can be coalesced with.
+ */
+int elevator_noop_merge(request_queue_t *q, struct list_head **insert,
+ struct bio *bio)
+{
+ struct list_head *entry = &q->queue_head;
+ struct request *__rq;
+ int ret;
+
+ if ((ret = elv_try_last_merge(q, bio))) {
+ *insert = q->last_merge;
+ return ret;
+ }
+
+ while ((entry = entry->prev) != &q->queue_head) {
+ __rq = list_entry_rq(entry);
+
+ if (__rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER))
+ break;
+ else if (__rq->flags & REQ_STARTED)
+ break;
+
+ if (!blk_fs_request(__rq))
+ continue;
+
+ if ((ret = elv_try_merge(__rq, bio))) {
+ *insert = &__rq->queuelist;
+ q->last_merge = &__rq->queuelist;
+ return ret;
+ }
+ }
+
+ return ELEVATOR_NO_MERGE;
+}
+
+void elevator_noop_merge_requests(request_queue_t *q, struct request *req,
+ struct request *next)
+{
+ list_del_init(&next->queuelist);
+}
+
+void elevator_noop_add_request(request_queue_t *q, struct request *rq,
+ struct list_head *insert_here)
+{
+ list_add_tail(&rq->queuelist, &q->queue_head);
+
+ /*
+ * new merges must not precede this barrier
+ */
+ if (rq->flags & REQ_HARDBARRIER)
+ q->last_merge = NULL;
+ else if (!q->last_merge)
+ q->last_merge = &rq->queuelist;
+}
+
+struct request *elevator_noop_next_request(request_queue_t *q)
+{
+ if (!list_empty(&q->queue_head))
+ return list_entry_rq(q->queue_head.next);
+
+ return NULL;
+}
+
+elevator_t elevator_noop = {
+ .elevator_merge_fn = elevator_noop_merge,
+ .elevator_merge_req_fn = elevator_noop_merge_requests,
+ .elevator_next_req_fn = elevator_noop_next_request,
+ .elevator_add_req_fn = elevator_noop_add_request,
+ .elevator_name = "noop",
+};
+
+EXPORT_SYMBOL(elevator_noop);
_