On 01/05/2011 11:19 AM, torn5 wrote:
Hello all
I am doing a test right now, I have about 200 outstanding commands (cat
/sys/block/devicename/inflight) at any time, I tried to go into
/sys/block/devicename/inflight/device and set queue_depth to 1, the file
is now set correctly to 1 and it previously was 1024, but open-iscsi

open-iscsi does not really control this. The scsi layer does. When someone writes to the sysfs file, the iscsi layer just calls a scsi layer function to set the queue depth to whatever was requested. The scsi layer then is supposed to make sure that it does not send more than queue_depth commands to the devices.



does not care about it and I still have about 200 inflight commands at
any time.

Isn't the queue_depth the max number of inflight commands?

Not exactly. A problem is that queue_depth is a scsi layer limit and is tracked in that scsi layer. But, inflight is a gendisk/block stat and is tracked there, so they mean slightly different things.

queue_depth - limit of how many commands that can be sent to the scsi device at any time.

block/gendisk inflight - how many requests are queued on the request_queue.

inflight can be higher because you can have lots of requests in the queue, but the scsi layer would only take queue_depth worth of them at any time to send to the device.




Am I supposed to logout and login again?


If you use sysfs no. If you use iscsiadm's node.session.queue_depth setting yes.

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