[PATCH] DAC960 request queue per disk

From: Dave Olien <dmo@osdl.org>

Here's a patch that changes the DAC960 driver from having one request
queue for ALL disks on the controller, to having a request queue for
each logical disk.  This turns out to make little difference for deadline
scheduler, nor for AS scheduler under light IO load.  But under AS
scheduler with heavy IO, it makes about a 40% difference on dbt2
workload.  Here are the measured numbers:

The 2.6.0-test11-D kernel version includes this mutli-queue patch to the
DAC960 driver.

For non-cached dbt2 workload  (heavy IO load)

Scheduler	kernel/driver	NOTPM(bigger is better)
AS		2.6.0-test11-D  1598
AS		2.6.0-test11     973
deadline	2.6.0-test11    1640
deadline	2.6.0-test11-D  1645

For cached dbt2 workload (lighter IO load)

AS		2.6.0-test11-D  4993
AS		2.6.-test6-mm4  4976, 4890, 4972
deadline	2.6.0-test11-D  4998

Can this be included in 2.6.0?  I know it's not a "critical patch"
in the sense that something won't work without it.  On the other hand,
the change is isolated to a driver.

drivers/block/DAC960.h

@@ -2333,7 +2333,8 @@ typedef struct DAC960_Controller
   DAC960_Command_T *FreeCommands;
   unsigned char *CombinedStatusBuffer;
   unsigned char *CurrentStatusBuffer;
-  struct request_queue *RequestQueue;
+  struct request_queue *RequestQueue[DAC960_MaxLogicalDrives];
+  int req_q_index;
   spinlock_t queue_lock;
   wait_queue_head_t CommandWaitQueue;
   wait_queue_head_t HealthStatusWaitQueue;