Re: qla2xxx: Conditionally disable automatic queue full tracking

[Michael Reed <mdr@sgi.com>]

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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>