[PATCH] CFQ io scheduler

From: Jens Axboe <axboe@suse.de>

CFQ I/O scheduler

drivers/block/Kconfig.iosched

@@ -27,3 +27,10 @@ config IOSCHED_DEADLINE
 	  a disk at any one time, its behaviour is almost identical to the
 	  anticipatory I/O scheduler and so is a good choice.
 
+config IOSCHED_CFQ
+	bool "CFQ I/O scheduler" if EMBEDDED
+	default y
+	---help---
+	  The CFQ I/O scheduler tries to distribute bandwidth equally
+	  among all processes in the system. It should provide a fair
+	  working environment, suitable for desktop systems.

drivers/block/Makefile

@@ -18,6 +18,7 @@ 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_IOSCHED_CFQ)	+= cfq-iosched.o
 obj-$(CONFIG_MAC_FLOPPY)	+= swim3.o
 obj-$(CONFIG_BLK_DEV_FD)	+= floppy.o
 obj-$(CONFIG_BLK_DEV_FD98)	+= floppy98.o

drivers/block/ll_rw_blk.c

@@ -1311,6 +1311,8 @@ static elevator_t *chosen_elevator =
 	&iosched_as;
 #elif defined(CONFIG_IOSCHED_DEADLINE)
 	&iosched_deadline;
+#elif defined(CONFIG_IOSCHED_CFQ)
+	&iosched_cfq;
 #elif defined(CONFIG_IOSCHED_NOOP)
 	&elevator_noop;
 #else
@@ -1329,6 +1331,10 @@ static int __init elevator_setup(char *str)
 	if (!strcmp(str, "as"))
 		chosen_elevator = &iosched_as;
 #endif
+#ifdef CONFIG_IOSCHED_CFQ
+	if (!strcmp(str, "cfq"))
+		chosen_elevator = &iosched_cfq;
+#endif
 #ifdef CONFIG_IOSCHED_NOOP
 	if (!strcmp(str, "noop"))
 		chosen_elevator = &elevator_noop;

include/linux/elevator.h

@@ -94,6 +94,11 @@ extern elevator_t iosched_deadline;
  */
 extern elevator_t iosched_as;
 
+/*
+ * completely fair queueing I/O scheduler
+ */
+extern elevator_t iosched_cfq;
+
 extern int elevator_init(request_queue_t *, elevator_t *);
 extern void elevator_exit(request_queue_t *);
 extern int elv_rq_merge_ok(struct request *, struct bio *);