Re: [PATCH 8/8] IB/srp: Make queue size configurable

[Jack Wang <xjtuwjp-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 09/13/2013 03:33 PM, Bart Van Assche wrote:
> On 09/13/13 14:25, Jack Wang wrote:
>> I tried your srp-ha branch in github,
>> echo string
>>> SRP2="id_ext=${THCA2_GUID},ioc_guid=${THCA2_GUID},dgid=${TGID_P2},pkey=${PKEY},service_id=${THCA2_GUID},can_queue=512"
>>>
>> to add_target failed with
>>
>>>   ib_srp: unknown parameter or missing value 'can_queue=512
>>> [  122.405385] ' in target creation request
>> Do I miss something?
> 
> Hello Jack,
> 
> Have you already tried the same command with "echo -n" instead of "echo"
> ? If I remember correctly the SRP initiator doesn't like a newline at
> the end of the string written into the sysfs add_target attribute.
> 
> Hope this helps,
> 
> Bart.
> 
Thanks Bart,

You're right, that is the problem, with -n option I can set can_queue
successfully.

But cat /sys/class/scsi_host/hostx/can_queue still show 63

Looks like it cause by the logic below:


>    /*
> 1870                  * Reserve credits for task management so we don't
> 1871                  * bounce requests back to the SCSI mid-layer.
> 1872                  */
> 1873                 target->scsi_host->can_queue
> 1874                         = min(target->req_lim - SRP_TSK_MGMT_SQ_SIZE,
> 1875                               target->scsi_host->can_queue);
> 1876                 target->scsi_host->cmd_per_lun
> 1877                         = min_t(int, target->scsi_host->can_queue,
> 1878                                 target->scsi_host->cmd_per_lun);

Could you give some hint on this, why we need to update can_queue and
cmd_per_lun here?

Cheers,
Jack
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