On Fri, 2006-03-10 at 14:16 -0500, Doug Ledford wrote: > > > > > command outstanding at a time, any driver that sets cmd_per_lun > 1 must, by > > > definition, be able to do it's own internal queueing and respect the limit > > > of 1 command at a time on untagged devices. > > > > > > Hmmmmmmmm are you sure? > > Try sending more than 1 untagged command to a device at a time. Instant > error. So, of course if cmd_per_lun is > 1 and the device is untagged it > must be queued somewhere. sure > Where may be a question now, but it used to be > either in the driver or the hardware. In my case, it was the driver and > that was specifically so that on command completion of an untagged command I > would have the next command ready to go and could stick it in the cards > QIN_FIFO during the interrupt handler, thereby improving things like round > trip time on tape drives so as to not interrupt streaming. If it's at the > mid layer level now, then you've taken away a driver's ability to do what I > just mentioned. drivers nowadays do NOT have queues (or if they do, they're left over and should be fixed). Of course a hardware based queue doesn't count in this sense... - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
