Adds the ability to enable / disable sorting of BIO requests queued within

CAM. This can significantly improve performance particularly for SSDs
which don't suffer from seek latencies.

The sysctl / tunable kern.cam.sort_io_queues provides the systems default
setting where:-
0 = queued BIOs are NOT sorted
1 = queued BIOs are sorted (default)

Each device gets its own sysctl kern.cam.<type>.<id>.sort_io_queue
Valid values are:-
-1 = use system default (default)
0 = queued BIOs are NOT sorted
1 = queued BIOs are sorted

Note: Additional patch will look to add automatic use of none sorted queues
for none rotating media e.g. SSD's

Reviewed by:	scottl
Approved by:	pjd (mentor)
MFC after:	2 weeks

sys/cam/ata/ata_da.c

@@ -130,6 +130,7 @@ struct ada_softc {
 	ada_state state;
 	ada_flags flags;	
 	ada_quirks quirks;
+	int	 sort_io_queue;
 	int	 ordered_tag_count;
 	int	 outstanding_cmds;
 	int	 trim_max_ranges;
@@ -449,6 +450,8 @@ static void		adaresume(void *arg);
 		 softc->read_ahead : ada_read_ahead)
 #define	ADA_WC	(softc->write_cache >= 0 ? \
 		 softc->write_cache : ada_write_cache)
+#define	ADA_SIO	(softc->sort_io_queue >= 0 ? \
+		 softc->sort_io_queue : cam_sort_io_queues)
 
 /*
  * Most platforms map firmware geometry to actual, but some don't.  If
@@ -670,10 +673,17 @@ adastrategy(struct bio *bp)
 	 * Place it in the queue of disk activities for this disk
 	 */
 	if (bp->bio_cmd == BIO_DELETE &&
-	    (softc->flags & ADA_FLAG_CAN_TRIM))
-		bioq_disksort(&softc->trim_queue, bp);
-	else
-		bioq_disksort(&softc->bio_queue, bp);
+	    (softc->flags & ADA_FLAG_CAN_TRIM)) {
+		if (ADA_SIO)
+		    bioq_disksort(&softc->trim_queue, bp);
+		else
+		    bioq_insert_tail(&softc->trim_queue, bp);
+	} else {
+		if (ADA_SIO)
+		    bioq_disksort(&softc->bio_queue, bp);
+		else
+		    bioq_insert_tail(&softc->bio_queue, bp);
+	}
 
 	/*
 	 * Schedule ourselves for performing the work.
@@ -999,6 +1009,10 @@ adasysctlinit(void *context, int pending)
 	SYSCTL_ADD_INT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
 		OID_AUTO, "write_cache", CTLFLAG_RW | CTLFLAG_MPSAFE,
 		&softc->write_cache, 0, "Enable disk write cache.");
+	SYSCTL_ADD_INT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
+		OID_AUTO, "sort_io_queue", CTLFLAG_RW | CTLFLAG_MPSAFE,
+		&softc->sort_io_queue, 0,
+		"Sort IO queue to try and optimise disk access patterns");
 #ifdef ADA_TEST_FAILURE
 	/*
 	 * Add a 'door bell' sysctl which allows one to set it from userland
@@ -1134,6 +1148,7 @@ adaregister(struct cam_periph *periph, void *arg)
 	snprintf(announce_buf, sizeof(announce_buf),
 	    "kern.cam.ada.%d.write_cache", periph->unit_number);
 	TUNABLE_INT_FETCH(announce_buf, &softc->write_cache);
+	softc->sort_io_queue = -1;
 	adagetparams(periph, cgd);
 	softc->disk = disk_alloc();
 	softc->disk->d_devstat = devstat_new_entry(periph->periph_name,

sys/cam/cam.c

@@ -110,6 +110,15 @@ const int num_cam_status_entries =
 
 #ifdef _KERNEL
 SYSCTL_NODE(_kern, OID_AUTO, cam, CTLFLAG_RD, 0, "CAM Subsystem");
+
+#ifndef CAM_DEFAULT_SORT_IO_QUEUES
+#define CAM_DEFAULT_SORT_IO_QUEUES 1
+#endif
+
+int cam_sort_io_queues = CAM_DEFAULT_SORT_IO_QUEUES;
+TUNABLE_INT("kern.cam.sort_io_queues", &cam_sort_io_queues);
+SYSCTL_INT(_kern_cam, OID_AUTO, sort_io_queues, CTLFLAG_RWTUN,
+    &cam_sort_io_queues, 0, "Sort IO queues to try and optimise disk access patterns");
 #endif
 
 void

sys/cam/cam.h

@@ -228,6 +228,9 @@ struct cam_status_entry
 
 extern const struct cam_status_entry cam_status_table[];
 extern const int num_cam_status_entries;
+#ifdef _KERNEL
+extern int cam_sort_io_queues;
+#endif
 union ccb;
 
 #ifdef SYSCTL_DECL	/* from sysctl.h */

sys/cam/scsi/scsi_da.c

@@ -145,6 +145,7 @@ struct da_softc {
 	da_state state;
 	da_flags flags;	
 	da_quirks quirks;
+	int	 sort_io_queue;
 	int	 minimum_cmd_size;
 	int	 error_inject;
 	int	 ordered_tag_count;
@@ -903,6 +904,8 @@ static timeout_t	damediapoll;
 #define	DA_DEFAULT_SEND_ORDERED	1
 #endif
 
+#define DA_SIO (softc->sort_io_queue >= 0 ? \
+    softc->sort_io_queue : cam_sort_io_queues)
 
 static int da_poll_period = DA_DEFAULT_POLL_PERIOD;
 static int da_retry_count = DA_DEFAULT_RETRY;
@@ -1140,10 +1143,15 @@ dastrategy(struct bio *bp)
 	if (bp->bio_cmd == BIO_DELETE) {
 		if (bp->bio_bcount == 0)
 			biodone(bp);
-		else
+		else if (DA_SIO)
 			bioq_disksort(&softc->delete_queue, bp);
-	} else
+		else
+			bioq_insert_tail(&softc->delete_queue, bp);
+	} else if (DA_SIO) {
 		bioq_disksort(&softc->bio_queue, bp);
+	} else {
+		bioq_insert_tail(&softc->bio_queue, bp);
+	}
 
 	/*
 	 * Schedule ourselves for performing the work.
@@ -1504,6 +1512,9 @@ dasysctlinit(void *context, int pending)
 		OID_AUTO, "minimum_cmd_size", CTLTYPE_INT | CTLFLAG_RW,
 		&softc->minimum_cmd_size, 0, dacmdsizesysctl, "I",
 		"Minimum CDB size");
+	SYSCTL_ADD_INT(&softc->sysctl_ctx, SYSCTL_CHILDREN(softc->sysctl_tree),
+		OID_AUTO, "sort_io_queue", CTLFLAG_RW, &softc->sort_io_queue, 0,
+		"Sort IO queue to try and optimise disk access patterns");
 
 	SYSCTL_ADD_INT(&softc->sysctl_ctx,
 		       SYSCTL_CHILDREN(softc->sysctl_tree),
@@ -1651,6 +1662,7 @@ daregister(struct cam_periph *periph, void *arg)
 		softc->flags |= DA_FLAG_PACK_REMOVABLE;
 	softc->unmap_max_ranges = UNMAP_MAX_RANGES;
 	softc->unmap_max_lba = 1024*1024*2;
+	softc->sort_io_queue = -1;
 
 	periph->softc = softc;
 
@@ -2133,9 +2145,16 @@ cmd6workaround(union ccb *ccb)
 			dadeletemethodset(softc, DA_DELETE_DISABLE);
 		} else
 			dadeletemethodset(softc, DA_DELETE_DISABLE);
-		while ((bp = bioq_takefirst(&softc->delete_run_queue))
-		    != NULL)
-			bioq_disksort(&softc->delete_queue, bp);
+
+		if (DA_SIO) {
+			while ((bp = bioq_takefirst(&softc->delete_run_queue))
+			    != NULL)
+				bioq_disksort(&softc->delete_queue, bp);
+		} else {
+			while ((bp = bioq_takefirst(&softc->delete_run_queue))
+			    != NULL)
+				bioq_insert_tail(&softc->delete_queue, bp);
+		}
 		bioq_insert_tail(&softc->delete_queue,
 		    (struct bio *)ccb->ccb_h.ccb_bp);
 		ccb->ccb_h.ccb_bp = NULL;