Messages in this thread | | | Subject | Re: Problem with aacraid driver in 2.5.63-bk-latest | From | Mark Haverkamp <> | Date | 13 Mar 2003 15:22:09 -0800 |
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On Thu, 2003-03-13 at 15:17, Doug Ledford wrote: > Mark Haverkamp wrote: > > > Does the cmd_per_lun element of the Scsi_Host_Template structure serve > > more than one purpose? > > Only when inappropriately abused by LLDD authors. The cmd_per_lun value > is suppossed to be for untagged devices only! If you have a tape drive > that doesn't support tagged commands but you want to be able to > internally have the next command queued up and ready to go when the > current command completes (in order to keep it streaming better), then > you can set cmd_per_lun to 2 and you will get two outstanding commands > for this device at a time. I used that so that in my interrupt handler > I could send the next command to the device before I passed the > completed command up to the SCSI layer. > > > In scsi_alloc_sdev it is passed into > > scsi_adjust_queue_depth. In the aacraid case this is 512. Later the > > aacraid driver (in aac_slave_configure) sets the queue depth to either > > 128 for tagged or 1 if not. > > That's where you are suppossed to set the queue depth on tagged devices.
Then it sounds like the aacraid driver could set cmd_per_lun to a small number like one since the real queue depth will be set later in aac_slave_configure.
Mark. -- Mark Haverkamp <markh@osdl.org>
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