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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