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

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

On 09/13/2013 11:24 AM, Bart Van Assche wrote:
> 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.
Thanks Bart,

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?

Cheers,
Jack

--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html