OS-73 do not do IO completions in the ISR
NEX-1889 mpt_sas should support 12G HBAs

*** 20,29 ****
--- 20,30 ----
  #
  #
  # Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  # Use is subject to license terms.
  #
+ # Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
  #
  
  #
  # The mpt_sas driver, as a pHCI driver, must specify the vHCI class it
  # belongs to(scsi_vhci).
*** 47,51 ****
--- 48,60 ----
  # To disable MPxIO on a controller whose parent is /pci@7c0/pci@0/pci@9
  # and the unit-address is "0" set:
  # name="mpt_sas" parent="/pci@7c0/pci@0/pci@9" unit-address="0" mpxio-disable="yes";
  #
  mpxio-disable="no";
+ 
+ # mpt_sas can do I/O completion in helper threads, reducing the amount
+ # of work done within interrupt context.
+ #
+ # mptsas_doneq_length_threshold_prop specifies the minimum number of
+ # I/O completions pending to handle them in a helper thread, a value
+ # of 0 causes all I/O completions to be passed to the helper threads.
+ mptsas_doneq_length_threshold_prop=0;