On 09/13/13 10:40, Bart Van Assche wrote:
On 09/13/13 10:06, Jack Wang wrote:
On 09/12/2013 06:30 PM, Bart Van Assche wrote:
On 09/12/13 18:16, Jack Wang wrote:
On 09/12/2013 12:16 AM, David Dillow wrote:
On Tue, 2013-09-10 at 19:44 +0200, Bart Van Assche wrote:
If this name was not yet in use in any interface that is visible in
user
space, I would agree that we should come up with a better name.
However,
the SCSI mid-layer already uses that name today to export the queue
size. To me this looks like a good reason to use the name
"can_queue" ?
An example:
$ cat /sys/class/scsi_host/host93/can_queue
62
Yes, I know it has been used before, but I'm torn between not
furthering
a bad naming choice and consistency. Foolish consistency and all
that...
I really don't like "can_queue", but I'll not complain if Roland
decides
to take it as-is.
What the allow range for this queue size?
Default cmd_per_lun and can_queue with same value makes no sense to me.
Could we bump can_queue to bigger value like 512?
Increasing the default value is only necessary when using a hard disk
array at the target side. When using a single hard disk or an SSD at the
target side the default value is fine.
Agree, from another side increasing default can_queue value is harmless
for single harddisk/SSD, but will boot performance for multiple LUN
attached to same host, so why not?
Increasing that parameter increases memory consumption for each path
between initiator and target. In a setup where both the initiator and
the target have multiple IB ports the number of paths can be large even
when only a single LUN is exported by the target. That's why I'm not
enthusiast about increasing the default value of the queue size.
(replying to my own e-mail)
Note: with the srp_daemon implementation available on github it's
possible to set the can_queue parameter for all logins initiated by
srp_daemon by adding something like the following at the end of
/etc/srp_daemon.conf:
a can_queue=512
See also http://github.com/bvanassche/srptools.
Bart.
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