Re: qla2xxx: Conditionally disable automatic queue full tracking

[Michael Reed <mdr@sgi.com>]

The LSI fusion FC driver did not exhibit the problem.  It doesn't
dynamically re-adjust the queue depth.  I have limited experience
with Emulex and cannot comment.

Thank you for offering to do the work.  I'll gladly review and test
anything you'd care to send my way.

Mike


Giridhar Malavali wrote:
> I will be more than willing to do these changes. Just curious, was  
> this seen on non qla2xxx drivers too.
> 
> -- Giri
> 
> 
> On Sep 24, 2009, at 12:15 PM, Michael Reed wrote:
> 
>> To answer your query, yes.  Ultimately, I believe the ml should be
>> modified to view a user space modification to a lun's queue depth
>> as an upper bound.  I don't care, much, whether the system dynamically
>> adjusts the queue depth or leaves it alone as long as it honors the
>> value programmed via user space.
>>
>> Are you volunteering to do the work?  :)  How can I help?
>>
>> Thanks,
>> Mike
>>
>>
>> Giridhar Malavali wrote:
>>> Hi Michael,
>>>
>>> Here are the patches..
>>>
>>> http://marc.info/?a=119828370000006&r=1&w=2 .
>>> http://marc.info/?l=linux-scsi&m=125201657106722&w=2
>>>
>>> Thanks,
>>> Giridhar.M.B
>>>
>>>
>>>
>>> On Sep 24, 2009, at 7:42 AM, Michael Reed wrote:
>>>
>>>> Hello,
>>>>
>>>> The purpose of the queue full tracking patch in qla2xxx is to
>>>> keep the driver from changing a user space override of the queue
>>>> depth back to what the driver believes is the "correct" value.
>>>>
>>>> The raid devices that we use have per raid controller queue depth
>>>> limits and have at times demonstrated, uh, bad behavior when
>>>> their queues are full for sustained periods of time.  SGI needs
>>>> to be able to set queue depth for a lun based upon access patterns
>>>> and performance requirements of the entire cluster and know that
>>>> it will be honored as an upper bound.
>>>>
>>>> Might you provide a pointer to the recently submitted patches?
>>>> I haven't followed linux-scsi in a while....  I'll be quite
>>>> happy to take a look.
>>>>
>>>> Thanks,
>>>> Mike
>>>>
>>>>
>>>> Giridhar Malavali wrote:
>>>>> Hi Michael/James,
>>>>>
>>>>> 	Patches were submitted to move queue ramp up/down code recently to
>>>>> scsi mid layer. With this change, I don't see a need for a module
>>>>> parameter to disable queuefull tracking  in qla2xxx driver. Andrew,
>>>>> mentioned that this got introduced to avoid wobbling behavior on  
>>>>> the
>>>>> wire due to queue depth modifications. Just wanted to check whether
>>>>> the same need to be done in scsi mid layer too.
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Giridhar.M.B
>>>>>
>>>>> --
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>