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

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 09/13/13 15:51, Jack Wang wrote:
> 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?

Hello Jack,

What is the value of target->req_lim on your setup ? The initiator 
limits the queue size to the target request limit because any attempt to 
queue more commands would cause the target to reply with "BUSY" anyway.

Bart.


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