On 03/15/2016 04:27 AM, Finn Thain wrote:
On Mon, 14 Mar 2016, Hannes Reinecke wrote:
On 03/14/2016 05:27 AM, Finn Thain wrote:
This setting does not need to be conditional on Atari ST or TT.
Without TCQ support, cmd_per_lun == 2 is probably reasonable...
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
---
drivers/scsi/atari_scsi.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
Index: linux/drivers/scsi/atari_scsi.c
===================================================================
--- linux.orig/drivers/scsi/atari_scsi.c 2016-03-14 15:26:45.000000000 +1100
+++ linux/drivers/scsi/atari_scsi.c 2016-03-14 15:26:55.000000000 +1100
@@ -750,6 +750,7 @@ static struct scsi_host_template atari_s
.eh_abort_handler = atari_scsi_abort,
.eh_bus_reset_handler = atari_scsi_bus_reset,
.this_id = 7,
+ .cmd_per_lun = 2,
.use_clustering = DISABLE_CLUSTERING,
.cmd_size = NCR5380_CMD_SIZE,
};
_2_ ? Are you being overly cheeky here?
I sincerely doubt the driver is capable of submitting two
simultaneous commands ...
Right. The LLD has LU busy flags to prevent a LU from being issued more
than one command.
Care to explain?
It seemed harmless and it is consistent with the all of the other 5380
drivers.
I don't know why it was done that way. Perhaps it was done to create a
pipeline. That is, to keep a small number of commands in the LLD issue
queue so that the NCR5380_main() work item does not have to terminate and
then get requeued needlessly.
Like I suspected.
While I'm aware of the reasoning, I sincerely doubt whether it makes
any difference in real life.
After all, a 'BUSY' return value still relies on someone kicking the
queue so that the next command can be submitted. So it's not much
different from using a queuedepth of '1' and use the 'official' way.
Have you done any benchmarking here?
Would be very interesting to check if it makes a difference in real
life ...
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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HRB 21284 (AG Nürnberg)
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