Re: [dm-devel] multipath_busy() stalls IO due to scsi_host_is_busy()

[Mike Christie <michaelc cs wisc edu>]

On 05/16/2012 09:29 AM, Bernd Schubert wrote:
> On 05/16/2012 04:06 PM, James Bottomley wrote:
>> On Wed, 2012-05-16 at 14:28 +0200, Bernd Schubert wrote:
>>> shost->can_queue ->  62 here
>>> shost->host_busy ->  62 when one of the multipath groups does IO,
>>> further
>>> multipath groups then seem to get stalled.
>>>
>>> I'm not sure yet why multipath_busy() does not stall IO when there is a
>>> passive path in the prio group.
>>>
>>> Any idea how to properly address this problem?
>>
>> shost->can_queue is supposed to represent the maximum number of possible
>> outstanding commands per HBA (i.e. the HBA hardware limit).  Assuming
>> the driver got it right, the only way of increasing this is to buy a
>> better HBA.
> 
> HBA is a mellanox IB adapter. I have not checked yet where the limit of

What driver is this with? SRP or iSER or something else?