[ofa-general] max_cmd_per_lun

[David Dillow]

On Sun, 2008-03-09 at 11:28 -0500, Tim Hadeen wrote:
> Hello,
> Default value of this is 63 and as per the name it stands per LUN. But
> is that the initiator limit or if we have 10 LUNs on target then total
> limits to 63 * 10 = 630 ?

max_outstanding_cmds = min(max_cmd_per_lun * number_of_luns,
				initial request credits)

"initial request credits" is given by the req_lim_delta in the
SRP_LOGIN_RSP reply packet.

You can find this value in the sysfs file
/sys/class/scsi_host/host${HOSTNUMBER}/can_queue, where host
${HOSTNUMBER} matches your SRP initiator.

max_outstanding_cmds can be temporarily reduced if the SRP target is
"lumpy" in returning request credits -- the initiator in 2.6.25-rcX will
not send a request unless it has the credits to do so.
-- 
Dave Dillow
National Center for Computational Science
Oak Ridge National Laboratory
(865) 241-6602 office