Re: Problem with aacraid driver in 2.5.63-bk-latest

From: Mike Anderson (andmike@us.ibm.com)
Date: Wed Mar 12 2003 - 19:50:46 EST

Alan Cox [alan@lxorguk.ukuu.org.uk] wrote:
> On Wed, 2003-03-12 at 23:55, Douglas Gilbert wrote:
> > /*
> > * Limit max queue depth on a single lun to 256 for now. Remember,
> > * we allocate a struct scsi_command for each of these and keep it
> > * around forever. Too deep of a depth just wastes memory.
> > */
> > if(tags > 256)
> > return;
> > ....
>
> I can see the memory consideration. However the thing can really handle big
> queues well. Possibly we should be setting the queue to 512 / somefunction(volumes)
> though to avoid the worst case overcommit here

I agree with Doug that the previous comment is out of date and we could
raise the value, but we also should never leave the function with the
possibility that the queue_depth is 0.

The patch below is something Patrick and I where discussing though I
believe he indicated that I should print out the value we where setting
the queue_depth to. It was only compiled and not tested on any devices.

-andmike 

--
Michael Anderson
andmike@us.ibm.com

 scsi.c |   32 +++++++++++++++++++++++---------
 1 files changed, 23 insertions(+), 9 deletions(-)

------

--- 1.96/drivers/scsi/scsi.c	Fri Feb 21 13:46:58 2003
+++ edited/drivers/scsi/scsi.c	Wed Mar 12 16:05:42 2003
@@ -926,15 +926,28 @@
 	/*
 	 * refuse to set tagged depth to an unworkable size
 	 */
-	if(tags <= 0)
-		return;
+	if(tags <= 0) {
+			printk(KERN_WARNING "(scsi%d:%d:%d:%d) "
+				"%s, tag value to small\n"
+				"disabled\n", SDpnt->host->host_no,
+				SDpnt->channel, SDpnt->id, SDpnt->lun,
+				__FUNCTION__); 
+
+		SDpnt->queue_depth = 1;
+	}
 	/*
-	 * Limit max queue depth on a single lun to 256 for now.  Remember,
-	 * we allocate a struct scsi_command for each of these and keep it
-	 * around forever.  Too deep of a depth just wastes memory.
+	 * Limit max queue depth on a single lun to 256 for now.
+	 * Too deep of a depth just wastes memory.
 	 */
-	if(tags > 256)
-		return;
+	if(tags > 256) {
+			printk(KERN_WARNING "(scsi%d:%d:%d:%d) "
+				"%s, tag value to big\n"
+				"disabled\n", SDpnt->host->host_no,
+				SDpnt->channel, SDpnt->id, SDpnt->lun,
+				__FUNCTION__); 
+
+		SDpnt->queue_depth = 256;
+	}
 
 	spin_lock_irqsave(&device_request_lock, flags);
 	SDpnt->queue_depth = tags;
@@ -949,9 +962,10 @@
 			break;
 		default:
 			printk(KERN_WARNING "(scsi%d:%d:%d:%d) "
-				"scsi_adjust_queue_depth, bad queue type, "
+				"%s, bad queue type, "
 				"disabled\n", SDpnt->host->host_no,
-				SDpnt->channel, SDpnt->id, SDpnt->lun); 
+				SDpnt->channel, SDpnt->id, SDpnt->lun,
+				__FUNCTION__); 
 		case 0:
 			SDpnt->ordered_tags = SDpnt->simple_tags = 0;
 			SDpnt->queue_depth = tags;

-
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